In order to define the email address that receives notification that someone from your club has requested to de-register and for you to action (approve or decline):

Click on Menu options: Organisation \ Organisation Details 

Under Contact Details heading \ Contact Email heading => enter in the email address that will receive the de-registration requests for you club

Example of email that you will receive if some requests to de-register from your club:

Click on the link in this email to access Play Football admin \ De-Reg requests, where you can approve or decline the request

The governing body above you (Assoc or Member Federation) will then need to 2nd level approve the request to complete the request.