A good place to learn to sing is in your local choral society. If that doesn't float your boat, try joining in at singarounds.

A good place to practice an instrument is at a local session.

The trick is to blend into the background until such a time as your confidence and ability are strong enough to do a solo performance. Better still, find a friend or two and form a duo/band.

Most solo performers have been a member of a duo or band in their formative years, and some still are. It works wonders for your confidence, because there's always someone to lean on if you make a mistake.