Things you'll need:
Download the DLC packages that you want to include. The map packages that I have included are all the maps that I have from Project Mimesis V3 that I found on my Xbox. The file type that the application uses is RXC. RXC is a Zip file with a different file extension, but to avoid confusion of files, changing it seemed like a good solution.
1) Open Halo 2 DLC Disk Creator V2.
2) Click the "Add" button, and with the file picker add your map package to your DLC list. [Repeat this step for all of the packages you want to install]
3) When you have your complete list, select "Export As Folder...", create a new directory and select it. You will be prompted to include the Halo 2 updater; if your Halo 2 isn't above version 1.0 you'll need the updater.
4) To install the maps to the Xbox, you can either burn the newly created DLC folder to a disk, or transfer the folder as an app to your Xbox. It's really up to you. Once you run it on your Xbox you'll see your list of maps with an update/install option. Install all the maps you want to have on your HDD.
And that's it! When you go on to Halo 2 you should have all of your selected DLC.
If you don't see your maps on Halo 2, you may need to update to V1.5.
I will be writing up a tutorial soon about how to create new DLC with your own maps. Until then I hope you will all enjoy being able to use Mimesis maps on a vanilla copy of Halo 2.
(Map Packages link updated. Part of the link was cut off)
Edited by Stolen Ruby, 24 June 2015 - 07:04 AM.