If you cannot edit a template in the courses overview, then you haven't got the right privileges yet.
Only if you have to role of Designer and/or Admin it can happen that the edit button is shown grey and you are not able to edit the course template. You are however able to create courses at the template.
In order to be able to edit the course template, you will have to do the following:
Give yourself access to the content libraries that are linked to the template.
Go to the tab User and find yourself in the list. Click on Roles and give yourself the Designer role if you haven't got that allready.
Then click on Update and go to the tab Designer. Via + Content library you can add the content libraries that are being used in the template you want to edit.
If you haven't got access to the tab Users then someone who has these rights has to add the content libraries to your account. Please ask the admin of the learning environment.
If you do not exactly know which content libraries are linked to the template, you can best select all content libraries if possible.