1. What you need

First of all, you have to download the "TOC-MOUL Installer" which you can find in the menu bar on the left. It will also be helpful if you already have Myst Online: URU Live (short: MOULa) installed, but it's not necessary.

2. Installing TOC

Now, you can run the Installer. If you have MOULa installed, the Installer will copy your files. If not, it will start the launcher in the so called "Repair Mode", which will download the files you need and might take some time.

Besides, make sure to create an account for TOC-Moul (also in the left menu bar). Then you can run the game by clicking on your shortcut, or running UruLauncher.exe, and play.