Check out Jeff Nippard and Dr. Mike Isratel on yt, they’ll give you all of the advice you ever need. Start a bulk with a high protein diet. Track your calories, it doesn’t seem important at first but it really is. Above all don’t get discouraged and be consistent. Progress will come and you’ve already taken the first step king👑
Look up a good beginner split on YouTube and do that at the gym. In terms of gaining muscle, increase your food intake and make sure you're eating enough protein. Also I have a lifting page on ig with basic guides on how to train each muscle group if you wanna check it out (@dev27lifts)