Does anyone know how I can paint a model on 3D builder?

[Reinboa]

I have been looking at videos on how to paint models but I am having trouble this one. This is my first time trying this.
You can download the model here: models.characters.body_variants._kz4.hgh_terrorist_1.textures.hg..
It is a Killzone Shadow Fall Black Hand terrorist model that I will soon try to figure out how to get to SFM and/or Gmod
Credit to the person who was able to obtain the model: https://luxox18.deviantart.com/