HOW TO REPLACE WITH ALL ALTERNATE TEXTURES:

1) Copy all folders in "alternate textures" (same folder this guide is in) and just paste it one folder up into "textures."
2) Overwrite existing files.
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HOW TO REPLACE ONLY A FEW TEXTURES:

1. Copy only the desired files
2. Manually replace the default textures with your new files in the "textures" folder. 
   (block items go in the "blocks" folder, items go in "items," etc.)

Or, alternatively: Just delete the files you DON'T want before copying/pasting the whole thing.
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MISC INFO

-If you want one of the textures to be different texture than what it is named, simply 
change the name of the file to match the texture you will be replacing.

-If the name has _alt in it, you will need to delete this part before copying the file over.

-If you are copying over anything animated, you will need to ALSO copy over the .mcmeta text 
file.