Monitize With Mobile CPA?

Hello. I'm am wondering how some people have that monetizeation for CPA on mobile devices where they get paid when somebody downloads a sponsored app. Like on Instagram I see things like "Flappy Bird Hack" and stuff all over and when I click the click it takes me to this webpage where I have to download an app. Obviously they are making money somewhere in this. But does anybody know how to do so? Like where can I sign up to get the API and make cash. Like what websites can let me do this?