I found some helpful links

Making Friends As An Adult / Backed By Research

Making and keeping friends as an adult


Someone once gave me some really good advice that I'd forgotten about until now: "If you're nervous about a party, or group gathering, when you walk in, look for the friendliest looking face in the group, and talk to them." This may not work for everyone but it really helped me and still does bring me comfort. I will do this next time I'm in a really big group and feel I don't really know anyone and feel nervous and clammed up.

Here's two more links I found helpful.

Gretchen Rubin's 8 friendship tips

5 habits to combat loneliness