After successful installation, you can find the app under System.
There are two tabs:
Jira Templates: System created templates
My Templates: Your user created templates
Click Jira Templates: and all the Jira templates available in your system are listed on left side bar.
Click on your selected template
Modify its content
Click Save after you’re happy with your changes
Restart Jira to apply new changes
My Email Templates
Click My Templates: and all your created and saved email templates are listed below
To Edit: Click on ✎ under to edit
To Copy: Click on 📄 to copy
To Delete: Click on 🗑 to delete
To Create a new email template.
Click Add: and a new page appears for you to fill in, to create a new template.