To "make it" means to become successful. For example, you can ask someone who's really successful this:
When did you first start to feel like, "Yeah, I made it?"
In some very competitive industries, like entertainment and the arts, people sometimes talk about "making it in this business":
It's hard to make it in this business.
When you talk about "this business" in a phrase like this, it means the industry that you work in.