Here is the simple answer. It's hard. It takes many small steps that also involve giant stepbackwards.

When I was in that sitution. I bought a notebook and wrote down how I felt, what my fears of the future where and what I wanted to happen. Then I wrote a list of all the things I had control over and things I had no control over that made me unhappy.

I focused on the things I had control over and then wrote a list of how I will resolve it. Overweight? Change your diet and hit the gym. Are you around people that put you down or drag you down? Remove them from your life. Can't talk to people? Then start doing so by taking small steps. First talk to people you meet at places like shops where they have to talk to you. Join sports clubs or activity groups.

If you are young and go to an educational institute. Look for all the social activities they do. Go to them and see which one you enjoy. I went to Acapella group once. I can't sing lol and quickly left. I ended up joining a group of runners and we used to hang around after training. Perfect time to talk to people.

Also I had a rule for myself. I would never be at home unless I was sleeping. I would spend as much time as possible in campus. From morning to night time. I would talk to as many peoople as possible, get to know them just for the sake of knowing them. I learnt very quickly even the best looking and most popular person is struggling as well. Everyone has a facade.

It's a journey that takes time. I don't want to write a massive essay. But if yopou want to talk more. DM me.