Wirelessly posted (iPhone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 2_1 like Mac OS X; en-us) AppleWebKit/525.18.1 (KHTML, like Gecko) Version/3.1.1 Mobile/5F136 Safari/525.20)
Yoy plug it into your computer and it will prompt you to restore from a backup. Just select the backup and you're done.
FYI it does take a little while so be patient.