Right click on model and select edit contents then a new window will open, u have to o be on move tool,right click on the minikit appearing on the screen select materials then click on the icon next to diffuse a context menu will appear click on replace texture and select your kit texture. Then click on render (it's thr bottom right icon on that window) or just click alt+shift+ctrl+R on the keyboard, when it finishes rendering go to file and save now return to the original window you'll find your minikit there.