I'm not smart enough to make a forger file for just this tattoo mod. To use this mod, you should download another tattoo mod, and copy and paste these textures into that mod.

Each folder comes with 3 .dds files (big, medium, small) and each size is as follows: big (1024x2048), medium (512x1024), small (256x512). 

Rename each of these images to the corresponding tattoo .dds images in a mod of your choice, and make sure that each size is the same (right click on the image and check its dimensions).

For example: If you are using the Ragnar Tattoo mod, and you want to substitute that tattoo texture for this one, then rename the big file "Ragnar_Tattoos_0", rename the medium file "Ragnar_Tattoos_1", and rename the small file "Ragnar_Tattoos". Then swap these new textures for the old ones. 

If this doesn't make sense, just pm me and I can explain in more depth.

I really did nothing, all credit should go to nfcintra and QuilLeeR for making actual tattoo mods with a forger script.