You will now see options pertaining to your email address in the central pane.
Choose “IMAP Accounts” at the top to access the email filters settings and then click on the pen icon on the right of the page.
You will then see a pop-up window with a form.
After clicking “Ok” the pop-up window will close.
To complete the process and activate the signature, you must now Save your changes, by clicking on the green floppy disk icon in the right-hand corner of the page.