First you will have to download the add-on by navigating to the Template Gallery Download Page. Select Free where you will be asked to continue and allow permissions.
Then you will be able to run the add-on by navigating to a Google Docs document and selecting the Add-ons tab at the top, and select Template Gallery and within that menu select Browse Templates.
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There a screen will appear with a categorized listing of the various kinds of templates that can be used.
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Once you find and select a template that you like, select the button labeled Copy to Google Drive. The File Type information below this button will let you know if the template you selected is a template for Google Docs or Sheets.
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After copying to Google Drive, the same menu will appear, this time with the blue button saying Open File. Selecting that will open that template in a new tab. You can now begin editing the template!
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