Can I plug an iPad directly into the time capsule and back it up or do I have to have a computer?

angcat,

Mobile devices cannot be backed up directly to the Airport Time Capsule.

The iTunes program on the computer is required for backup.

In addition to backing up to iTunes on a computer, you have an option to backup directly to iCloud.

See this Apple Support document for more details:

http://support.apple.com/kb/ht1766