Double-click on the user in left pane then you would be able to see the permissions for that specific user.
Based on your screen shot, I dont think you have opened the user you want to configure the permissions.
As per the steps in the link you have referred, if you follow below step, you should be able to provide the right permissions
5. Select the data user. - MAKE SURE YOU DOUBLE CLICK ON THE USER 'DATA' YOU HAVE CREATED
6. From the right-hand pane, select the Permissions tab.
7. Expand the content tab and then select the customers row.
8. Click all the checkboxes that represent the permissions.
9. Click the Save button located in the top menu bar (located above the Path heading).