To earn a commission from any Amazon books you promote on your website:
1. Sign up for an Amazon Associates account:
2. They have a tool that will generate a link that you can put on your website. This will be under your Associates account, in a section called "Build Links". This is actually a pretty cool tool; they have all kinds of links with graphics, without graphics, etc. available.
3. Copy-and-paste those links into your website's HTML code, or into your HTML emails!
That's all there is to it!