This looks super cool and I genuinely really want to play it, and I sincerely do not want to be mean, but these might be genuinely the least helpful installation instructions I have ever seen.
EDIT:
OK - after making an attempt to follow the instructions again I decided to spend another 6 hours looking into how to get it working myself (since seemingly nobody can resist being a condescending goofnugget and assuming that this is the most basic thing in the world (its not)).
Firstly get Parallel Launcher and of course the actual mod, I wouldn't even bother for a second trying to patch it with Floating IPS as they suggest, because if its anything like my experience it is just way too confusing to even try doing.
Once you have Parallel you will want to get a ROM for Paper Mario 64 itself, in my experience trying to actually use your own copy of the game doesn't work (but if you CAN, then 100% do that as I am not very experienced in using that so it likely was just user error?), if you need a ROM you will want specifically the version from Roms Games as other ROM's just refuse to patch. After that you will need to navigate to "Add single ROM" and first add the vanilla version of Paper Mario 64 (of course after unzipping it) and then you should just be able to launch the mod file itself and Parallel will automatically add it and patch it for you into the modded version of the game.
Was it worth it? ABSOLUTELY - this mod is actually really goddamn fun! But god spending 12 real life hours figuring this out really gave me a newfound general dislike for a lot of people, like seriously if you go and search like I did you will find plenty of people asking how to do this and just getting the most condescending and jackass responses I have ever seen (not for the Paper Mario community specifically, but just in general). I am sorry for everyone who had a similar experience in that regard, but I hope this was able to help at least someone (even if it will likely get removed).
Edit 2:
If you are using a Nintendo Switch Pro controller, use Steam to launch Parallel if you are having an issue where its constantly doing inputs. This isn't an issue with the mod, just something I learned that would likely be helpful to anyone trying to play the mod (Still loving the mod btw, you did great!)