You can find your referral code on any book page by clicking on one of the share options on a book page. I use the Twitter link, but the email link also works. It will look like this https://www.inkshares.com/books/lost-generation?referral_code=c6b4e1d8. When a visitor to the site clicks your link, you will be the referrer, which means if they purchase a book you will receive credits. It is also a great way track who is sending people to the site to buy your book (you can see referral metrics in the dashboard.)