The LaTeX template is designed to create a .tex file, which you would then use pdflatex or xelatex to create a PDF with. You would not be using Scrivener’s PDF printer, as it does not have a built-in LaTeX engine.
For this template to work the way it was designed, you need to select “Plain-Text (TXT)” as the file type, and use the compile format provided in the project in the left sidebar.
If you need manuscript formatting, you will need to make some adjustments to use a different document class, or maybe just some changes to your preamble to use different fonts and double-spaced lines, etc. There may be some guides on the 'net for how to do this.
As for where to make changes in Scrivener:
- Right-click on the “LaTeX (Memoir Book)” format in the left sidebar and duplicate it. This way you keep the original safe. You can rename it at the top to something else, like “LaTeX (Manuscript)”.
- Click on the “Text Layout” pane, and here you will find where the documentclass is set. This template is intentionally very simple so that you can easily customise it.
- The Front Matter folder is a good place to organise most of the preamble. My way of thinking is that the Format should change the biggest things: the document class, packages necessary for the big picture, and so on. Front Matter is better for things the project will need for itself. Consider you might choose to save this custom Format global, rather than in the project itself, so that you can use it on future books as well.
But in the end it is entirely up to you. Some might not want to have anything in the format and have all of the preamble in the front matter folder. There is no wrong way, so long as it all prints out in the correct order.