To install the mod, follow the instructions:

Step 1: copy the data.win of this mod
Step 2: go to C:\Program Files (x86)\Steam\steamapps\common\DELTARUNEdemo (assuming you got deltarune from steam)
Step 3: paste the data.win file of the mod into whatever your deltarune directory is, (i recommend u make a backup of the game's data file) and agree to replace the file, and your done!