The referral URL can be seen in the statistic area.
1) Login to your account
2) Click "Submit Banner/Get Code"
3) Click STATISTIC for one of your active banners in the "Ad Sizes" box.
4) On the new page in the INFO box (bottom part) you will see;
Send possible users to .......
This is the URL with your personal referral code behind. It's the URL you want to use to signup other users and receive Bonus for each referral.
The other "Referral Page" show what sites show your banners and where clicks to your site come from.