Affiliate bonuses

[Iceware]

I'm reading How I made my first million on the internet and how you can too! and Ewen says to offer additional bonuses of your own with your affiliate products but he doesn't tell you how to go about doing so. I'm wondering if anyone knows how to set it up or knows of a video or something that shows you. I don't understand how to know if someone goes to the affiliate site and buys the product or not. I know I can track and check if they do. I'm not sure how to go about doing this since I'm not the one who is packaging the download. please help