What should i do to loose weight and gain muscle?

[idksoup]

So, a bit of background, I'm 5'6 ", 14 and 145, I wanted to come on here to get an unbiased opinion on how I can lose weight without looking like a twig. I have access to a gym and any food I would want. If some people could just give me some advice on how to build muscle while losing fat, that would be helpful