You will have to go to:
Home >> Summary of Security Realms >> myrealm >> Roles and Policies tab:
Expand the Global Roles tree:
take any of the available roles , let us say: Requester
Click on the view and modify roles:
under Roles Condition : Click on Add Condition :
From the List: select Groups
Then Under the Group name type: mygroup
Click Add
Then Choose : “or” as the to add the multiple groups to a single role.
Click on save.
you might have to restart the server after making changes to the roles.