[Pseudoscience-is-malarkey (OP)]

I was given a Gibson Acoustic SJ-200 Western Classic Acoustic Guitar and I think it would be unappreciative to let it collect dust. I can play the piano and sing more or less, but I have to admit I find it difficult to pluck strings in any sophisticated manner.

[Bored chemist]

"Any advise on guitar learning?"
I'm sure some advise on learning it.
Are you looking for advice?

[Colin2B]

"Any advise on guitar learning?"
I'm sure some advise on learning it.
Are you looking for advice?

I can indeed advise 
My advice would be to look online, lots of sites (or should I say sights?) offering lessons.
On the other hand, he could buy a case for it, then it won’t collect dust

[alancalverd]

I find it difficult to pluck strings in any sophisticated manner.

You and several billion others.

Andres Segovia said that the guitar is a very easy instrument to play badly, and very difficult to play well.

My teacher said if it doesn't hurt for the first two years, you aren't doing it right.

For the last 70 years I have hovered well above the base camp pain level but never approached the Dolly Parton foothills, never mind Segovian altitudes.

A Chinese chef once explained the art of making Chinese pancakes: " Mix flour, salt, water, roll out thin and cook in hot pan with no oil. Very simple, very difficult. Take five minutes to learn, take ten years to get right."

If all else fails, sing loud and play quiet.

[LisaShafer]

Find a good and skilled teacher

[Subjecould]

If you already know how to play the piano and have an ear for music, then take a couple of lessons with the basics or just a video on the same resource and then you just need to practice. It is best to choose a couple of melodies and memorize them. When you succeed, look for new ones and so on. You still need to be able to play for yourself and not build a life around it.

[Cassy0110]

watch some videos on youtube

[JesWade21]

Don't put off learning basic music theory (circle of fifths, major scale positions, etc.) because it will help you with both composition and improvisation.

Practicing for 10 minutes every day is preferable to practising for an hour once a week.

Learn other people's songs, but also try to stretch your creative mind and create your own, even if it's just a simple melody or chord progression.

[Sheilataylor]

When I learned to play the guitar, I went to a teacher in my town; she managed to make me play quite well in a few months. You simply need 30 - 60 minutes a day to learn a bit. In home conditions, I don't recommend you to learn because it will be very hard and will take a lot of time.

[Zer0]

It seems Complicated, but it Ain't.

Just need to learn 14 Chords.
7 Major - ABCDEFG.
7minor - abcdefg.

P.S. - Strumming is a good pastime, but you will definitely need Help to get it in Tune first before you begin.
Orelse it's gonna sound Gothic!

[alancalverd]

14? Surely not! And since most wind instruments are played in "flat" keys (F, Bb, Eb, Ab) you may need a whole lot more.

The great thing about rhythm guitar is that you only need to learn 4 chords to accompany most songs. If you can play G, Em, Am and C, you can get a capo d'astro to shift the whole lot up by a semitone at a time, to cover whatever key you want to sing in. It works for pretty well every folk song. For rock'n'roll, E, A and B7 will suffice.

If you want to go further, learn to barre with your first finger (this is the bit that hurts) and learn F, F7, Bb6 and C7 in the first position. You can then use those shapes anywhere on the fingerboard and get away with most rock, jazz and big band accompaniments and the entire Beatles songbook, and folk singers will think you are a professional because you don't faff about with the capo between numbers.

When you get used to the pain, try major 7ths and 9ths, and sling in the occasional Diminished - a very useful "passing" chord for trad jazz, dance music and torchy ballads. The next 60 years will be full of fun and gigs, and you will lose the fingerprints of your left hand. This last can be an embarrassment at US Immigration, especially if you also play jazz bass, because that will erase your right hand prints too. But you will never be short of friends.

Best song ever: Sultans of Swing. To be played at my funeral, please. Just look at the rhythm guitar fingering on the studio You Tube to see what I mean about moveable barre chords.

[alancalverd]

And another tip from an ancient jazzer. Fight your way through the pain barrier and practice proper classical fingering!

We all get lazy and use the left thumb on a narrow-necked guitar. A couple of weeks ago I developed tendonitis and a painful "trigger thumb", but still have enough wrist flexibility to play a 6-string barre with my thumb immobilised in a splint, and haven't missed a gig!

Real pessimists should study Django Reinhardt's fingering, just in case you lose one or two!

[jasonlava]

I learned a lot from just messing around with it every day, trying out chords, and playing along to my favorite tunes. It was a bit of a struggle to get my fingers used to the strings, but sticking with it really paid off. My advice? Start with the basics and don't rush.

Learning an instrument takes time, and it's okay to go at your own pace. Plus, it feels awesome when you finally get a song right. If you're looking for tips on where to begin, you can read here [...] about other experiences and opinions. It's geared towards beginners and could be just what you need to get started.

[Zer0]

Short advice...
First learn how to Tune it.

ps - Makes no sense to proceed with driving lessons, when one cannot even unlock the vehicle.