To install a skin on MC for Mac (roughtly)
1. Download the MJP file. It's a text file with a URL inside. Use TextEdit or something else to open it and copy the URL.
2. Paste the URL into a web browser or something and download the ZIP file that has the SKIN inside it.
3. Go find your skins directory for your version of MC. It should be at a path similar to: /Users/<your user name>/Library/Application Support/J River/Media Center 26/Skins/Standard View . To get there, you probably have to open Finder and use the "Go To Folder" option. Because for some stupid reason, Mac wants to hide your Library directory from you. The Go To menu item will get you there though. I use "~/Library" which is a shortcut to "my user name>/Library" .
4. Unzip the Skin ZIP file into a new directory inside the Skins/Standard View/ directory. This should happen automatically when you use an unzip program, as most skins create this new directory. For example, if the skin is named "Bob", it will create a directory named "Bob" where ever you unzip it.
At this point, MC should see the new skin and be able to use it in the View > Skin menu.
Experiment a bit and you'll get it to work.
Brian.