If you are not able to edit a group then it could be because:
a) The user you are logging in with does not have sufficient permissions in Blue Prism (i.e. is not a member of the defined Blue Prism Administrators Active Directory group)
b) You are trying to change the AD Group of the Blue Prism Administrators, and this needs to be done in the System -> Single Sign On screen.
Hope that helps.
Chris (BP Support)