Well, the reason I copied the text from the Help file myself is that it is the very latest, updated text, and not the same as the section you quote.
The piece I quoted tells you exactly where the file is, and exactly how to access it and edit it.
I hope someone corrects me on the next bit, if I am wrong, but in the process I described in the Help you are creating a new template within the RTF Editor based on the Normal.rtf file, and presumably you can put your boilerplate text and graphics in that. Or copy that template and use the copy for your boilerplate.
The point is, the Normal.rtf file is the style template, and you can create as many templates as you like from that, and copy existing templates to create new templates, all of which can be 'washed' with the Normal.rtf style template using the File | Update Styles menu option.
So, if you want a boilerplate that incorporates any changes you decide to make to the Normal.rtf styles, import the Normal.rtf file into a new template in the RTF editor, make your style changes as required, export that template to update the Normal.rtf file, then edit the same template in the RTF editor to include your boilerplate text. When you need to change the Normal.rtf styles again, import the Normal.rtf file into another new template in the RTF editor, make the changes, export that back into the Normal.rtf file, then open your existing boilerplate template and use the File | Update Styles option to wash the style changes into the template.