Template file means just an Excel file with the formatting done…
In that make all the columns as per your requirement (column datatype, width, etc) then store in the project folder itself
At the end of process while creating a output file, simply copy that template and paste the data using Write Range in the target sheet and make sure you uncheck the the checkbox in properties panel and have the Range as A2
The below link is for the mini-tutorial for output report enchantment and it has a workflow that shows the above-mentioned steps. Just make the template as per your requirement.
Output Report Formatting using a Template
Hope this helps!