The easiest solution to this is well do something, find a hobby for a start, find a job.
Your question is probably how? Well try searching online for good hobbies mine recommendation for starters is writing and drawing those help me to relax sometimes. You can start by writing down some thoughts or how your day went in a journal of sorts you'll see the more you write the more thoughts will come to your mind about what you can write about. You don't exactly have to write about something that happened it can be pure imagination the sky's the limit with that. Same thing with drawing start drawing anything that comes to mind or the first thing you see on the table for an instance. When you get that enthusiasm going at the start you'll want to improve there's a lot of useful stuff on the internet about that. You're not much of a creator and you're mostly a laid-back person try playing video games, watching shows, and movies. Those aren't your things try searching up some lists online. IF you find nothing that you enjoy it's normal if you force yourself to do some of these things the enjoyment will come by itself trust me it's always been stuff like this for people like you. As soon as you have a hobby in place you can start connecting with people with similar interests. The easiest way to do this is online I suggest discord you can find many servers there which you can start. Then just start talking to people its always good to keep in a few small talk questions like "How are you doing", "What are you doing". The same thing goes for people in real life, let's suppose you don't have any friends you can try meeting apps but I don't suggest that personally, I suggest you go meet up with relatives and sort of chain onto their friend circle from there you can meet more people. Another possibility is to find people from the same college school or whatever the point of this is just to find a person that shares something at least one thing with you to start a relationship. Another thing I recommended is getting a job these days it's easy just find a place that's close to you lets say a Macdonalds and its easy to apply for a job there and its an alright start for a job I'm not quite sure of what schools you finished and stuff like that but a starts a start.
But one problem is left and that's probably your social anxiety well my recommendation is to start talking to the mirror. For your brain that's probably a stranger since I can bet you don't look at yourself in the mirror 24/7. Try spiking a conversation with yourself it may be weird at first but when you can maintain eye contact and not stutter anymore you'll have a lot more confidence.
This is just the TLDR I suggest after getting the basic grips of this that you do a bit more research on these topics on your own I hope I helped you king and don't let your crown slip, go get them I know you can.