Time Machine backup is too large for the backup disk

my TM wil not back up! It states that this backup is too large for the backup disk. The back up disk requires 573.50 GB but only 225.23 GB are available. The TM needs work space on the backup disk, in addition to the space required to store backups. Upen TM perferences to select a LARGER backup disk or make the backup smaller by excluding file.

Okay I;m sorry but obvioulsy I dont get this. I've never called Apple for help! I have every product they sell practically including Protection Plans I never used and no one will help me with this. My MAC is starting to have black or white screens and i can hear it running but it will not do anything so i have to reboot it, it screws up Enturage and then I have to rebuild that ( 5 times this year) anyway... I would like to back everything up- can I delete everything on the Time Capsule or Time Machine; god I dont even know what it is called Im so MAD... help if you can please. I'm going to have to take this to the genius people at the store and probably buy another computer but like before they will not save my files.