an old saying goes, to make a friend, be a friend. Another, Art thou lonely brother? Share thy little with another, ok I found the quote. John Oxenham
Art thou lonely, O my brother?
Share thy little with another!
Stretch a hand to one unfriended,
And thy loneliness is ended.
As alluded to above, find clubs and social groups that share interests, join, meet them and see what happens. You might need to attend things a few times before you fit in because most groups meet occasionally and when they do they tend to reacquaint themselves with people they already know. Expect that and just hang around conversations until you find you have something to contribute. And, the others, seeing you are listening in might ask your opinion on something.
The essential thing is to get out and get with other people. Nothing can happen if you isolate yourself.
I've known boys that have never asked a girl out, especially the ones they like the most. Fear of rejection, right?
OK, here's the key to that. If the first girl isn't interested, you don't really know why. Her current situation might not allow her to accept your offer. Not your fault, ask another girl. There are tons of girls that grieve over not being asked out. Keep asking and you will find one. Then, you will both be a lot happier.
Basically, don't be the least concerned about rejection, whether it's a girl or anyone else. Let it go and move on to the next prospect.
Other people are in your situation no matter what it is. There are almost 8 billion people on the planet and we can be in contact with more than half of them. I guarantee that many of them are in a situation similar to yours.
OK, go out - meet people. it will be interesting if nothing else. Good Luck