Once you've finished editing your textures, save everything.
You want to do this so you can prevent cropping issues with the texture, since anything too much outside the range will get cut off. Then, get rid of the existing sprite and keep the new one (assuming they're on separate layers).
When editing textures, try to make them line up with the existing sprite as best you can. Although if you do use, if the save screen comes up and the type at the bottom says. But you don't have to use, you can use something else like Photoshop.
You'll have to look up a tutorial on how to use, since I won't be explaining it here. NET Framework 4.7.1, so I'll put a link to that too. I use, since I can put all of the textures into one window and scroll through them at the top. You'll need some kind of image editor that supports transparency, and preferably can open up multiple files at the same time. Make sure you don't modify ANY of the filenames, or else you won't be able to import them back into the game. Once it's done, go to your folder, and ALL of the textures in that sharedassets file should be there. The explorer window should pop up now you need to click on the folder you just made ONCE so it's highlighted in blue. Go back to UABE, and then on the far right, click the button that says "Plugins." Another window will pop up. Next you have to make an empty folder, and name it something (preferably the same name as the sharedassets file you're editing for convenience's sake). Now don't click ANYTHING else in that list, or else you will deselect all of those textures. Everything should now be highlighted blue. Now you have to hold down SHIFT and then click that. Now that you have everything sorted, click on the very first thing that you see with the type "Texture2D." Then scroll down until you find the very LAST thing with the same type. If the column is too small for you to be able to read the file types, click on one of the lines next to the "Type" option and drag it out so you can see. As you can see, the asset types are in that column below the word "Type." You may have noticed that each sorting option is separated by lines. At the top, there's a button somewhere that says "Type." Around there, you'll also see a button that says "Name." Click on "Name" first, and then click "Type." Everything in the window is now sorted by type, but also alphabetically, since you clicked on "Name" first. The first thing you need to do is sort all the assets in this new big window by type. Now the question is, how do you modify the textures? Well, I'm getting to that. Sharedassets5 (1.3 and up) - Secret ending assets. Sharedassets3 - The random objects that appear after a game over. This is the most important one out of them all. Sharedassets2 - Literally everything that you find in the school. Sharedassets0 - Default Unity stuff, no need to go here. Now, you're probably wondering what all of the sharedassets files contain, so I'll sort it out for you: If you get this, scroll all the way down, click the last one, and then press OK. assets file saying that you're trying to edit and unknown database type, and you'll get a whole list of Unity versions.
Before you open these however, if you're modding a version that's 1.3 or greater, a window will pop up upon opening a.
Now there are 4 files (5 if you're modding versions 1.3 and up) that you can open in this directory: sharedassets0.assets, sharedassets1.assets, sharedassets2.assets, sharedassets3.assets, and sharedassets4.assets (plus sharedassets5 if on versions 1.3 and up). Then navigate to the Baldi's Basics copy you just made, and go to the folder called BALDI_Data. In UABE, in the top left, click File, and then Open.
Once you have UABE up and running, make a copy of your Baldi's Basics directory that you can use to mod the game. It's IMPORTANT that you get the correct version by using the link below.
To modify textures, you're going to need to download UABE (Unity Assets Bundle Extractor). Well, I suck at making tutorials, so I'll just make this text guide. Everyone's been requesting me to make some kind of tutorial on how to mod the game.