To install textures, place the "textures" folder supplied by the mod in the following folder:
steamapps/common/Fallout4/Data.

You need to make sure the file structure is correct within the textures folder e.g.
steamapps/common/Fallout4/Data/textures/clothes/GreaserJacket.dds.

When you place texture files here, the game will take them from this folder instead of from the textures.bsa file.

To uninstall simply remove the folder which has the textures in. Note, if you just remove the .dds files but not the folder, when you run the game you will find those textures missing, so you need to remove the folder as well.