*By using this guide, I am assuming that you already have the MOD that you have chosen to install*
*This guide applies in .dff and .txd MODs only, and NOT sound mods, etc*
*ALWAYS remember to MOD at your own risk, if not sure about a certain MOD, ask!*
Open up your GTA SA IMG Tool. I use Spark IMG Tool because in my opinion, it is the easiest to use (download link below)
Click "Open" and find your GTA directory. Once you've found your GTA Directory, find the folder called "models" and find the file that's called "gta3.img".
Open this file, and you should see something like this.
Now open up the folder where you saved the MOD that you have downloaded and look at its file name. Usually there will be at least one .txd file and one .dff file.
It is recommended to ALWAYS have a back up copy whenever you are installing a MOD. If you don't know how to make back up files, checkthe 2nd post for a tutorial in making back up copies of the original .txd/.dff files.
Whether you made a back up or not, the next step is to drag (or copy and paste) the .txd and .dff files of the MOD you are trying to install. Just simply drag and drop it into Spark. And click Save, by either clicking File, then Save. Or just simply pressing the Save button at the top part of the window.
Once all this is done, go ingame and check if your MOD was succesfully installed.