You would have to purchase updated navdata from Navigraph:
http://www.navigraph.com/www/default.aspCreate an account, place credit on the account then on FMSData you attempt to download the one you want. This will then prompt you to pick whether you want the current cycle, or if you want to get a years worth which actually gives you 13 cycles at a discounted price.
Once you have activated a cycle or a sequence of cycles, you can download all the different types of data format for that cycle as many times as you like. You would want to PMDG all products one, which may well be an installer.
This will update all your PMDG products such as 737, MD-11 etc. You can also grab the package for your flight planning software (if you own) such as Flight Sim Commander on the same cycle at no extra cost.
Hope that helps.