Security groups mass assign

Hi,
Im having trouble finding the way to enable security groups, mass assign. I disabled when i installed the CRM but now, i need it and i cant find the way to enable it again.

I already check the roles and tab/modules display.

What i am missing?

Thanks in advance.

Regards,

How did you disable it?

Yeah, me too. Been trying to find a way to disable it. How did you do it?