I am trying to back up my iPad via a external hard drive. how do i do this with my cloud being full

Back it up to your Mac, you can't use an external drive.

Backup using iTunes to your Mac > Back up your iPod touch, iPhone, or iPad

There are ways to free up iCloud storage > How to free up iCloud storage space

Are you trying to backup to an external HD connected to your computer, or a wireless HD interfaced to an iPad?

Mac - How to Move the iPhone & iPad iTunes Backup folder to an External Hard Drive

http://osxdaily.com/2011/03/05/how-to-move-the-iphoneipad-itunes-backup-folder-t o-an-external-hard-drive/

How to Change the Location of Your iPhone Backup (Mac)

http://ismashphone.com/2012/05/how-to-change-the-location-of-your-iphone-backup. html

Windows - Change iPad default backup location

http://apple-ipad-tablet-help.blogspot.com/2010/07/change-ipad-default-backup-lo cation.html

Windows - Changing IPhone and iPad backup location

http://goodstuff2share.wordpress.com/2011/05/22/changing-iphone-and-ipad-backup- location/

 Cheers, Tom 😉