You may enter free form notes from the Agent Desktop. When enabled, it will show on your screen while you are in "In Call" or "Wrap up" status.
Click the notepad button to access the agent free-form notes UI.

You will be presented with the Notes screen where you may input any useful information.

Click OK once you have finished entering the information.  

The Note field is a free-form field. It is limited to 4000 characters.

 You will be required to specify an account number when entering a note for calls without account numbers.