I have a creator's block on the mod and I don't know what to do with the mod, I was about to abandon it until I still saw some interest in it right now. Installation is take the data folder from the mod, go into the Gaijinizer folder, then the game_en folders and put the data folder into it so you overwrite it. I even put installation instructions into the files too, at this point I may have to rush the mod a little bit.
As for how to start the route, do geno as usual until you drink the potion for Mother Rabbit's infection. Then get an item outside the convenience store before interacting with the nekomata, later on search for another item at the start of Arachne's nest and finally choose to not shoot the guy so you don't abort the modded route.