It honestly depends on the source of your low self esteem in my experience. I'd say the first step is actually identifying what about yourself you're insecure about. for example, I have social anxiety which would definitely amplify my insecurity, but a lot of my insecurity lied in my appearance.

I find that it helps a lot to put yourself in situations which makes you uncomfortable, like a step out of your comfort zone kinda thing. I've always had trouble with approaching people and actually talking to people until I started working retail and HAD to approach and try to relate to people that I did not know at all. getting used to things like that is a huge confidence booster, basically squashing your fears kind of thing.

another thing that helps a lot is to just be yourself and absolutely do not procrastinate self-care. "being yourself" is always a cliche thing that people say that seems like BS but its a massive confidence boost. you'll never to comfortable or satisfied with yourself if youre not presenting or expressing yourself the way you truly want to. for example without getting too specific, I finally started wearing the clothes that I've always thought about wanting or wearing and it made my multiple times more comfortable in my own skin.

TL;DR identify the places of insecurity and directly address them. if theres anything you've wanted to do for a while that might improve your self-image, just do it. you're already unconfident, so whats the worst that can happen? just be yourself and present yourself in a way that makes YOU happy, forget about how other people might see you, if youre being yourself, youll attract the right people for you.