1. Login to your Google Drive account.
  2. Open the Template File for which you want to get the FileId.
  3. Copy the FileId from the URL.

For an image or PDF:

  1. Right-click on the image for which you want to get the FileId.
  2. Right-click and select Share. 
  3. Click Copy link and Done.
  4. Paste the link into Notepad or another application. It looks like this: https://drive.google.com/file/d/1f448sqhwDWqet****UJk2X5_1TMF0Lg/view?usp=sharing
  5. Copy the FileId from the URL (for example, highlighted in red).