Credit Card, Invoice and Publicity

Hello, I’m doing an Android game and I have just two questions to get it done: my game has purchasable content, how do I allow the future players to buy this purchasable content with their credit card? How this whole credit card and invoice works? Second: how do I put publicity in my game? That’s all. Answering this and I’ll have no problems left. ^^ Thank you guys. (there are other alternatives to) … they have SDK for transactions, etc.