If you chose signup.yoursite.com, enter: signup
Enter host.launchrock.com in the Hostname field.
Congratulations! Your CNAME record is now configured to point to LaunchRock.
If you have trouble configuring your CNAME records, you can check out the Linode tutorial page. Or, view a sample message to use when you contact Linode for assistance.
Once you've modified your A records, it may take up to 72 hours for changes to update live.