To install this skin, extract the contents of the zip file to a location you can find later, preferably the desktop 
The unzipped folder includes 12 .dds files (a-L), 1 folder which will be the skin name, and 1 installation.txt file 
 
Move the folder and its content into your main installation of DCS A10C using this path 
..\DCS A-10C\Bazar\Liveries\A-10C 
 
Move all of the .dds files and add them to the zip file called A-10.zip 
..\DCS A-10C\Bazar\World\textures\A-10.zip 
 
enjoy