How can I create an AWS CodeCommit Template ?

First, follow this guide - and make sure you've set up SSH access to your CodeCommit repository. 
When you create your template in env0 - you will need to create a template using the "Other VCS" type.
For the URL - you'll need your CodeCommit user name, it will look like this - (using the values from the tutorial above) -
To complete the setup - you will have a place to set the SSH key for the template, where you'll need to copy and paste your private SSH key for the repo (created in the tutorial above as a local file).