Practice. Visualization exercises. We have this weird idea that people are just supposed to be good at social interactions. Like, people will spend their entire life honing their skills at sports or baking or chess and then expect you to just be cool with talking to strangers.
Here's a basic visualization exercise. Visualize people you're comfortable around, see them smiling and happy, maybe laughing, but notice how they make you feel, how comfortable and relaxed you are, and as you do that imagine there's a bright colorful energy around them and the more you feel those feelings notice how the energy becomes brighter and more vivid. Do that until you've really got a feel for the taste of that energy. When you think you've got a really good hold on it, create a physical trigger for yourself that you would feel comfortable doing in the presence of other people; maybe it's tapping your cheek or waist, maybe squeezing your forearm, or maybe drawing a symbol like a heart in the palm of your hand. But take that energy and imagine a bond forming between doing that trigger and that nice relaxing energy wrapped around the people you've been thinking about. Really let that bond solidify and link up.
Then, break. Do something silly like waving your arms and doing a raspberry or something to erase the scene you've been thinking about.
Then repeat. And do that a few times every day, as many times as it takes for you to feel comfortable with it.
And then, once you think you've got a handle on it, imagine yourself walking up to someone you want to feel comfortable around and do the trigger, and imagine that energy reaching out and wrapping around them and pulling them into the safe and comfortable space you keep people you're okay with being around. Really focus on the feeling and vibrance of it all.
Just keep practicing doing that. And then eventually, try it live.