Bulk add users to RLS Role

HI,

My client has over 5000 users. Each user is mapped to a specific location and can only see data for his particular locations. This is naturally done through the user_security table. 

The RLS works, but I wonder how can I add those users to the role on the service in a bulk?

Can it be done or it needs to be done manually?

If we do it via AD group, do we still need the dim_security table?

Regards,

Rosa