How do I start?

I'm a 16m and I'm looking to lose weight and get fit. I have belly fat and a gut, and honestly I'm just looking to lose it, and start gaining muscles, because I just really need a confidence boost. But everytime I step into the gym, I just get insecure cuz there's always a bunch of The Rocks walking around, and I just leave cuz I'm so intimidated. And I rarely feel motivated either, but I still really wanna get fit. How do I do this? And what exercises are recommended?