1. Open the screen 
  2. Click the 'magnify glass' icon on the left side for the required document
  3. The details of the selected document will open.  You can now enter the remarks and save. 
  4. When you exit you will be returned back to the 'Document Follow up Screen'. 
  5. Click 'refresh' in order to see the remarks entered 
For further guidance, please refer to the below screen shots: