Go to your "Settings" page in your 22Slides control panel and click the "Set Up a Custom Domain" button in the "Domain Name" section.
Enter your domain name in the blank and click the "Setup Custom Domain" button.
Login to IWantMyName.com and click the "number of domains you have."You have X domains" link.
Click "Install new service".
Use the search box at the top right to find "22Slides".
Click "Install 22Slides".
That's it, you're done! Your domain should start working within an hour or two, however it's recommended to wait about 12 hours before sharing your site with others, since different parts of the world might take a bit longer to see the changes you just made.