Go into Settings in Donorfy and search for 'Email Server Settings' - you will see a form like the one shown below - choose 'Gmail' as the Pre-configured Email Server

Next, enter your Gmail email address and password 

Click on Save Changes

Once you have done that press the Authorise Gmail button

You will then be taken to a Google form to authorise Donorfy - once you have completed that step you will be returned to Donorfy and will see a message similar to the one below

Click on the OK button to complete the process.
Once you have clicked on OK it will take you to your Home screen.

Occasionally an error can occur when authorising your Gmail account - see this article for help with that