Need to delete old backups from B2D in backup exec 2012

Hi All,

I am new to backup exec i face a challenge today i.e., my disks are full and i want to delete older data from the disks , i mean i have set retention period of 90days now we are changing it to 56 days and i want to have data of only last 56days rest of the data i want to delete , how i will be able to do it and also please advise how i can set override option so that after 56 it will start overriding the data.

Please help me out !!!

Thanks,

Nayab