All of the friends I have I know from other friends or met from working with them. So, for me, it is through old friends, or through work.
Take up Latin dancing join a beginners class ... great fun, challenging .. and by its very nature social social social.
I just have friends at work and at a bar I use to visit when I was separated from my husband.
I do not consider any of the people at church my friends but I just go there to worship God.
My niece is a friend in a way though I am related to her, I think I would still be friends with her without being her dad's sister. For me friends just happen.
Coming to a place like this is a great way to practice your communication skills and broaden your interests. Then you can either make your new friends here or take those skills on the road and use them on meat people.
Talk to people! Go play pool!