How do i (26M) build up more courage to walk up to people and talk to them?

Never been in a relationship before. Shot my shot a couple of times but wasn’t lucky enough. Last time was when i was having a few drinks with my mate, and he said he’ll get the tab if i went up to talk to the person eating alone at the bar. I did, she declined, and said she had a boyfriend but we had a conversation for about 15 mins.
There’s been a couple of times i’ve wanted to walk up to a person and tell them they look pretty, i’d like to hang out sometime, grab a drink or something but i just chicken out. I know it’s not because i’m afraid of getting rejected, but i also don’t know what it is. Do i need more alcohol in me to go ask them? Maybe i just need to pick up a hobby and see if i can meet some people like that.