Jordan Brough Stuff I found online.

Use GoDaddy Domain with Tumblr

1. Login to GoDaddy’s Domain Manager
2. Select the domain name you would like to edit
3. Set Nameservers to “I want to park my domains.”
4. Enter Total DNS Control
5. Edit the A (Host) record for Host Name ‘@’
6. Enter Tumblr’s IP address (72.32.231.8) as the ‘Points to IP Address’
7. Go to http://www.tumblr.com/customize and setup your custom domain in the Info menu
8. Enjoy (or wait for DNS to propagate, then enjoy)

More information - http://www.tumblr.com/docs/custom_domains