Go to Assignments.
Select Assignments from the site Tool Menu.
Select Permissions.
Select Permissions tab from Assignments Actions Menu.
Modify the permissions for the roles listed.
Check the box next to each permission you would like to allow for a given role. (Deselecting a box will remove the corresponding permission.)
Note: You may see different roles listed depending on the roles that exist in your site. A role must be present in the site in order for you to modify its permissions.
Select Save.
Select Save button to apply changes.