Simplest way I've found to get to the template is to upload it.
I know that sounds strange, but bear with me;
- Go to actions on the main navigation bar and select 'Load Periodic Project Report template'
- This will open a pop-up asking you to confirm date format to use
- Once selected the template will load and provide you a link to navigate to the document itself
- Follow the hyperlink and you can then access the template to customise it and save as the original file name (I tend to save the original somewhere else first just in case)
Hope that helps.