Very Easy to do
Download the Megalist to a place where you can find it later
Open TT Designer
Open the IR Library Manager
Select the Remote Tab from the top menu bar
Select Import
After you select import find the file that you downloaded and select open
A window will open up and ask you if you want to Keep, Keep All , Replace, Replace all.
I select Keep all so you can keep the files that you already have and it will add the new ones.
When finished I usually go to File and Save as and make a new name for the library.
When in the TT open the new library and you should be good to go