the instructions:

open the deltapatcher.exe provided (or use your own homegrown version)
open the folder where undertale is installed
in the undertale folder you should see a file called "data.win"
in the "original file" box in deltapatcher navigate to the data.win file
in the "xdelta patch" box put the data.xdelta file provided and click "apply patch"

you shouldn't have to but you should probably back up your save file just to be safe

you can now play my 15 second long mod

to uninstall the mod:

delete the modified data.win file in your undertale folder
go to undertale on steam
click the gear icon and go to properties / installed files / verify file intergrity
this will reinstall the missing game files

if in doubt just watch mysticslime's tutorial it's easier to follow probably
