A texture MAT (or MAP) file is used like a skin on 3D models in DAZ Studio. Once you locate these 2D files you'll be able to create your own custom skins for personal use. In this tutorial I direct you where to find the files and how to go about editing them and applying them to your 3D models. Some experience with DAZ Studio and Image Editing programs is required. This tutorial is hosted offsite and can be found at the link above.