Could someone make sure I'm making a hexed poster model the correct way?

Earlier today, I decided to create a set of WW2 era Posters based off of a template uploaded to the old gmod.org addon site.

What I’m trying to understand, is a simple explanation on hexing models in a step by step format.

I already have VTFedit installed and I made a rough VTF file.

(This is what the image looks like)

I just don’t know if I’m doing this correctly and what other custom files I have to make for each image.

Resources I’ve looked at:

https://garrysmods.org/download/4847/posterzip------(Reuploaded Poster file with confusing directions in the description.)

Test Run files

https://www.dropbox.com/s/fu4ldcdth1fqxve/Rationing%20Coffee%20Soldier.tga?dl=1

https://www.dropbox.com/s/iw8t65ykql8gjva/Rationing%20Coffee%20Soldier.vtf?dl=1