Brian
Just adding to DistEds full instructions ....
Don't use the 2013 CD on the new PC since CDs are not updated over time and if you follow DistEd's route you will get the current version with little updating.
But note that you will not automatically get the 2013 version you have on the existing two machines (assuming you did not upgrade them to 2014 which the Version ID shows you did no) but the 2014 version.
If for some reason you want the 2013 version just say so and I'm sure we can find a direct download link for that version updated as far as the 2013 version went and save you from running the CD and updating that through lots of sub-version changes.
Note also that your new PC will almost certainly come with a trial version of some security program -- often Norton but not always -- and you need both to uninstall this AND run a special cleanup tool you can get from the website of the installed program. So when you know what you new PC is and what trial software it comes with, let us know and we can point you to the tool you need.
Hope that helps.