Hang in there! It took me a long time to figure it out and I'm still constantly learning.
1. Be your own best friend. Let it be okay to be yourself, and by yourself. Treat yourself well. Do things you like. Spend more time outside.
2. Be friendLY. Smiles, small talk, eye contact. Welcome people into your world.
3. Discover common interests. People like to talk about stuff they're proud of and offer advice to people who are also into it. Astronomy, photography, cars, hiking, art, etc.
4. The Dale Carnegie classic "How to Win Friends and Influence People" is worth a read.