QuickBMS:https://www.dropbox.com/s/lu1258ggfh5... Everything else pretty much:https://www.reddit.com/r/Underminers/comments/3s0wch/tutorial_easiest_way_to_get_into_the_files/
The thing that was at the end of the vid:https://www.youtube.com/watch?v=t8xrB... Written tutorial:Get WinRar if you don't already.
Right Click on Undertale.exe in it's Steam Directory.
Extract it somewhere.
Now download QuickBms which can be found on Reddit Via Underminers. Extract that to a folder. Now wherever you extracted Undertale go there and copy and paste "Data.Win" to wherever QuickBms got extracted.Make a folder called UnderBackup in the folder with QuickBms. Now click on QuickBMS.exe and select items in this order. 1."Yoyogames.bms" After clicking that the promt will re appear again. 2.This time click on "Data.Win" 3.It will reappear one final time and this time you need to go into the emtpy Underbackup folder and click save.Now when it finishes go to the TXTR folder to see the sprites that you can edit/view.After you finish your editing do the same excact proceses except click on "Reimpmort.bat" instead of QuickBms.exe.Now when it finishes copy and paste it over to where you extracted UnderTale.exe to test.