Hi Dylan and Casanova, hopefully I can help you at this attempt, I don't have too much time., and likely won't visit the site again for the next couple of days. The template, now organised into 13X13, represents a key to a code already entered in the main grid. It's just a case of which cells in the main grid you need to highlight. The 6th word (penultimate word) of the instruction is 4 letters (I think already mentioned on this thread) and should be considered as its constituent letters.
One option, from this point, is to physically remove all 41 occurences of those letters from the template (similar to last week's puzzle) and see what is shown in the main grid when you overlay the template (provided they match for size !).
Coincidentally, I recently watched again the story of John Nash, I think it's called 'A Beautiful Mind'. Much of his delusional experience was that he was asked by the CIA to find embedded Russian codes in newspapers and periodicals. Which was quite hard to watch really, but it is a similar form of coding to that of the theme.