Ok, Thank you for requesting some help. Here I can help you and get your problem fixed.
As he PM'ed me IG asking help. I didnt have time to help as I had to go take a shower. So I quickly told him to make a Help request.
Ok, So what you need to do is follow these steps
Step 1.) Download a IMG Editor [I suggest spark, Link will be at the bottom of the page]
2.) Download the mod for the skins, Then open it up, There should be some files somewhere with a .txd and a .dff on the end of it.
3.) Open the IMG editor and press CTRL+O then, Locate your Gta San Andreas file. In this case. It should be in this directory.
C DRIVE > Program files > Rockstar Games > Gta san andreas > Models > gta3.img [Double click gta3.im]
4.) Drag all the .txd and .dff files from the download into the IMG editor. So simply select the .txd and .dff files and just drag them into the IMG editor.
5.) Press CTRL+S and then that should save it. Close the IMG Editor.
6.) Choose the skin in game and check to see if it worked, For my skin mod it was the Azteca skin with the black jacket and a cap on it. The skin that it rplaces is in the video.