Nero Cover designer help required - newbie

I’m trying to get to grips with the Cover Designer in Nero 7 … Got some DVD covers to print but the DVD template is set up for a ‘standard’ box only. Can someone please tell me how to create a template for different sized cases (e.g. slimline or the more bulky 6 disc holding boxes)
As stated newbie to Nero 7 and this forum - joined today.
TIA of kind responses :confused: