The Fan Ages, or Ages created by players of Uru, can be visited using either the UAM Shard or the Deep Island Shard. The UAM Shard offers one simple installation method that is explained on its website. The Deep Island Shard on the other hand, offers two installation methods: for Offline and Online use. As these are two slightly different ways to install the Deep Island Shard, I will start by explaining the difference between the two.
Installing Deep Island for Offline use gives you everything that is in Uru Complete Chronicles plus the ability to install Fan Ages using the Drizzle program. Use this version to explore the Ages in more detail as most of the KI-commands are available, including the flymode commands. Take pictures from viewpoints that you would't be able to reach in MOUL or the Complete Chronicles.
Installing Deep Island for Online use gives you everything that is in Uru Complete Chronicles plus the Fan Ages using the Nexus. In this version the typical MOUL additions are available too, like the Garden Ages, the Pod Age, Minkata, Jalak Dador, the Bahro wedges and the 12 sparks. This version is mostly used to give guided tours of new or updated Fan Ages as this version also has the online multiplayer component like MOUL.
Deep Island uses the Uru Complete Chronicles game as a basis, so you will need that game installed before you can setup Deep Island. The following steps work under win7 and probably other versions too. Following these steps will let you make a copy of the original Uru CC folder, which has the benefit of not having to install Uru CC again in case you need to reinstall Deep Island at a later time for some reason.
Also, the installations of Deep Island Offline and Online cannot be mixed; you can't put them in the same folder together. Each of them needs to be installed seperately (copied actually) into it's own folder.
Copy the 'Complete Chronicles' folder to another location on your harddrive, like from: 'C:\GOG Games\Myst Uru Complete Chronicles' to: 'C:\Games\Uru-Deep-Island-Offline'. Make sure the name of the folder does not contain any spaces or using Drizzle will fail later on. Then you will have to copy the files from the di-patcher.zip file (that you can download here.) into this directory. Delete the file Uru.exe (It is only used by the online version of Deep Island) and start the game by running UruSetup.exe.
At this point, Deep Island does not have any Fan-Ages yet, it is the same as in Uru CC at the moment. To add Fan-Ages you need Drizzle. Drizzle is a java program, so you need java installed for that. Download Drizzle here. After download, unzip the file in your Deep Island Offline folder, it contains only one file: Drizzle31.1.jar. Run Drizzle by double-clicking it unless you have an archiver like winrar installed, in which case you need to right-click the Drizzle file and choose "Open with" and then "Java".
Win10 and newer versions may not offer the "Open with" option. Win11 will throw even more hurdles at you by flagging the drizzle file as unsafe and blocking it from letting drizzle save files to disk.
The first time you run Drizzle, make sure you set the path where Drizzle will find the "Deep Island Offline" folder under UAM Settings, Pots folder. (Beware, the select folder dialog will allow you to select a folder with spaces in the name. However, downloading of ages will still fail in that case.) After that, click on "Get Latest List" and you can select an Age that you want to add. Next, click on download to add the Age to your Deep Island Offline folder.
If you prefer, you can rename UruSetup.exe to Uru.exe and start the game using this Uru.exe instead.
The steps are almost the same, except that you need an account at the forum of the Guild of Writers first: Create an account.
Copy the 'Complete Chronicles' directory somewhere else, like from: 'C:\GOG Games\Myst Uru Complete Chronicles' to: 'C:\Games\Uru-Deep-Island-Online'. Make sure the name of the folder does not contain any spaces or using Drizzle will fail later on. (Although Drizzle is not needed in the online version for adding most Ages, Drizzle is still used for adding the Myst 5 Ages.) Then you will have to copy the files from the di-patcher.zip file (download here) into this directory, overwriting the files that already exist. Next, start the game using Uru.exe and provide your GoW username and password. After that, you should be able to create an avatar and play the online version of Deep Island.
Read more on how to install Deep Island at the 'Guild of Writers' forum.
The offline version uses the Drizzle program (more info) to install and update Fan Ages, while in the online version this is done using the nexus. The online version does not use Drizzle for that. Drizzle is still used however, for adding Myst 5 Ages and Ages from other Cyan games.
The Guild of Writers forum tells you to remove the original "complete Chronicles" installation afterwards, but I have left it installed and can run them both if I want to.