How to start riding a bicycle in your 40s, if you never developed bike skills? How to snowboard, if you never developed snowboard skills?

… Do it; suck. Do it more; suck less.

“How to Make Friends and Influence People” is a great & classic book about giving people social room, focus, support, and attention with genuineness and humour (“influence” isn’t meant in a manipulative sense). Effort and attention are required, and practice, but that’s the cost of change and improvement.

Find ways to lower the stakes.

Make new friends with others that have underdeveloped social skills and figure it out together.

Do things in a group in some activity that won't put the spotlight directly on you and where you can observe others.

Explore therapy where odds of rejection are pretty low since you're paying them for coaching.

I think noticing how children play is very instructive, but if you don't have good social awareness that could get you in trouble. Kids haven't internalized all the baggage you and I might have about social rejection and awkwardness yet. They just confidently say "hey I like your bracelets will you tell me what they mean to you?" and if it doesn't pan out this time they play with someone else. It's the social anxiety / awkwardness that usually makes people the most uncomfortable, not the atypical interactions. Kids don't have that at all.

I like classes for meeting new people for a few reasons. First, there's a structure around the activity which doesn't force you interact all the time. Second, you're not entering an established group as the one new person. And third, you're all going through a shared experience which naturally helps form bonds.

If you're really hard up for social skills, and you like being around silly fun people and are okay acting silly yourself, I recommend taking an improv class. Any introductory improv class is basically kindergarten games to help you realize how low stakes socializing can be.

But I also realize improv isn't for everyone. In that case I recommend finding an activity you might be interested in and taking a class in it. If you aren't sure what you're interested in, good news! That means you get to take all the classes until you find one you like.

Even if there's no classes for your activity, anything that can be done out of the house and with other people probably has a community built around it. Use your interest in the activity as leverage to expose yourself to that community.

https://www.empathiceurope.com/ has free courses/trainings on empathic listening skills.

Spend some time on that website, see what you can dig up on specific skills, and then test using them in real life.

That site skews heavily towards therapists, and has a lot of woo-woo. It is clearly not THE answer.

But it is A answer. Enough to give you a framework to get started.

It's one of those things: the world doesn't care (unless you are really attractive of course), so you'll have to choose: Do I want to put even more effort into this and/or fake it 'til you make it - or do I want to be alone?