You already know how to use Deltapatcher. Select your original data.win file in the Undertale folder.
Select the patch. Press the patch button.

Your original data.win NEEDS to be Undertale 1.08 for this to work.

All sprites, code, etc. are included in the patch.

Additionally, you have to replace your UNDERTALE .exe file with the one included in the folder.

Have fun killing (or detaining) Shayy!

This is the improved version of the mod btw