In order to edit certificate templates that are already created, you can:
Click on “Settings” from “Navigation bar” on the left side of your screen
Select “Certificates” from the drop-down.
Click on the drop-down menu indicated by the three dots against the template that is to be edited
Select “Edit”
Here, you can:
Change the template and select a new one if needed.
Edit the certificate content.
Change the name of the certificate template.
Save the template and generate samples of template.