If you are on PC, you must find you community folder and unzip the RAR or ZIP file into your community folder. If there are two files, you must place both inside the community folder for the scenery to properly work.
If you are on Xbox, unfortunately this website is useless to you. Stay tuned for any possible marketplace releases!
To install, open the PMDG Operation Center V2, select Aircraft and Liveries, Livery Utilities, select PMDG 737-600 under Installed products and Variants / Models, and click Install from PTP file, and select the livery you downloaded.
Any free addons are available right here through the links in the top right, or you can find my profile on Flightsim.to. My payware products are currently available on Simmarket, and we are actively looking into become a Microsoft Flight Simulator Marketplace Vendor in the near future. D66 is now available through the flightsim.to link too!