Click on Configuration.
Click on Sales Channel Settings then the Sales Channel you want to edit the Listing Template for.
Click on Manage Listing Template.
Find the Template that you want to edit and click on the pen and paper on the right hand side of the screen.
Now you can edit the Template but you cannot change the account, Market Place or the category. If you wanted to edit these fields you will have to create a new Template.
When you have finished editing click Update at the bottom of the screen.
If all of the fields were filled in correctly, congratulations you have successfully edited a Listing Template. If there is something wrong, an error message will appear and it will say if a field was filled out incorrectly and you might need to make a adjustment to it.