You go to an advertising network (be it something like push / pops/ native, or the big guys like FB and Google)
You find a product that you'd be ready to promote (chances are you'd go with the CPA model) , sign up in an affiliate network, get a link
You create creatives that will be launched (hopefully you'd look them up in a spytool)
You lunch campaign after campaign (in a selected ad network) for your own budget
You analyze the performance, and hope for the camapign to convert
And then you rinse and repeat.
The key is persistence, as there is no secret sauce.