Adding fields to BP

Hello All ,

I am new at CRM and I have a question :

What the best way to add fields to BP. I need to add some additonal fields/tables to BP.

We need to classify our Bp according to group and sub-group.Where user select the group the list of available subgroups should be displayied according to previous selection. Additionall every BP may belong to one or more groups/subgroups.

Thank you ,

Rika