What you downloaded are 99.9% .aswcs files. Standard skin files contains .asws extensions. You’ll notice the difference. Standard .asws skin file, you can just put into standard avast! > data > skin directory among all the other skins.

Files that you downloaded (.aswcs) are also skin files but self-extracting files. Just as Vlk said, you just have to click those files twice and start them. They will automaticaly extract standard skin files into your default avast skin directory.

Hope this helps !

Cheers !