[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