Go to Assignments.
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Select Assignments from the site Tool 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.
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Select Save button to apply changes.