When you select a template then it starts new automation with a filled-in answer for the automation name, trigger, condition, and action that accomplishes a specific use case.
For example, you select the "Auto assign issue" template. Enter the name of automation and select the project. All other fields are pre-filled: trigger, condition, and action. So, you can review and do minor edits as you see fit.
Don't forget to enable your automation after entering and selecting all values.