Restricting user to display products in product category

Hi Folks,

I want to restrict some users to view products of only 3 product categories.

I read in an SCN post that authorization group needs to be maintained in ECC and needs to delta downloaded to CRM.

There was no auth group maintained in ECC.Should I /can I create one in CRM?

Auth object COM_PRD_CT is used to determine whether user is allowed to create/display/change /edit products of a product category.

Should this auth object be assigned to users/user group?

Pls suggest steps and how to achieve this

Regards

Jaya