-PVMEditSharp (Part of SA Tools) [SA Tools Download][mm.reimuhakurei.net]
or
-PVMEdit [PVMEdit Download][info.sonicretro.org]
-An image editor like Paint or Photoshop (To make the textures)
-The BetterSADX Mod:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=299808681

I will be using this as an example:

Here we go.

1. Once PVMEdit has downloaded, move it to any where on your PC (i recomend the SADX game folder)
2. Open PVMEdit inside the Pvmdit!.zip folder
3. Click the File tab, then Open
4. Search for the PVM files (They are located in /steamapps/common/Sonic Adventure DX/system some where in your pc) the pvm files are existant in the Vanilla Steam Release and the HD Mod
5. Once you have found your pvm's, select the one you want to edit (It's hard to tell what pvm file is for what model in the game it may be a case of trial and error, unless you only want to edit a certain character inwhich the character's pvm files have their name as the file)








6. Important!: Make a backup before editing any PVM! Unless you want to risk having to reinstall the entire game or have your character look the way you don't want it to
7. Find the texture you want to edit
8. Create a replacement texture, but remember:
-Make sure the dimensions are the same
-Make sure certain parts of the texture are in the right place (May required some trial and error)
-A good idea is to work off the original texture and edit it from there (To get the original texture as a image file, right click on the texture in PVMEdit and click export, it will save as a BMP)



Example image of Sonic's SADX Shoe texture:







9. When you have your replacement texture ready (Must be in BMP format!), right click on the existing texture in PVM edit and click import, then find your new texture
10. Click file, save and then you're done!
[/previewimg]

Any questions ask below!
The knowledge i have shared is all my own (Believe it or not, i did exactly this when i was 8)

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=298309316
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=299808681