welcome to pc, anne. you''ll find lots of friends here i think!!! i'm not sure if you meant that are retired or just tired of trying to make friends and are younger. here are some things that may help you (i liked the suggestions you already got, btw):
join a group of something you're interested in like a bowling league, hiking, etc
like already said, try to do some volunteer work. it may open some doors for you when you're not even expecting it.
go to places that you have some interest in..like i love reading and the arts, so it's barnes and noble for me. made some good friends there.
take a class at a school in a subject that interests you. most people there will have similar interests and that's a good jumping off place to make friends that way.
why do you think "you don't know to to make friends"? can you elaborate?