DOCS: Adding instructions about how to add external apworlds

WebHostLib/templates/supportedGames.html

@@ -31,6 +31,9 @@
     {% include 'header/oceanHeader.html' %}
     <div id="games" class="markdown">
         <h1>Currently Supported Games</h1>
+        <p>Below are the games that are currently included with the Archipelago software. To play a game that is not on
+        this page, please refer to <a href="/tutorial/Archipelago/setup/en#adding-new-worlds">this
+                section of the setup guide</a>.</p>
         <div class="js-only">
             <label for="game-search">Search for your game below!</label><br />
             <div class="page-controls">

worlds/generic/docs/setup_en.md

@@ -136,6 +136,25 @@ are rolling locally, ensure this file is edited to your liking **before** rollin
 when running the Archipelago Installation software. If you have changed settings in this file, and would like to retain 
 them, you may rename the file to `options.yaml`. 
 
+### Adding new worlds
+
+If you are generating locally, you can play with worlds that are not included in the Archipelago installation. 
+The worlds are packaged as `.apworld` files. To add a world to your installation, click the "Install APWorld" button in
+the launcher and select the `.apworld` file you wish to install. Alternatively, you can drag the `.apworld` file onto the
+launcher, manually add the `.apworld` file to the `custom_worlds` folder of your Archipelago Installation, or double-click 
+the file itself. After adding a new world, it will function like the worlds that are already packaged with 
+Archipelago.
+
+We strongly recommend that you make sure that the source of the `.apworld` is safe and trustworthy before playing with a 
+custom world.
+
+#### Adding alternate versions of included worlds
+
+If you want to play with an alternate version of a game that is already included in Archipelago, you will need to manually
+replace the original `.apworld`. To do so, go to your Archipelago installation folder and navigate to the `lib/worlds` 
+directory. Then, create a backup of the `.apworld` or the folder corresponding to the game you want to play an alternate 
+version of. Finally, replace the base `.apworld` (or folder) with the alternate `.apworld`. If you want to play the original
+again, replace the alternate version with your backup.
 
 ## Hosting an Archipelago Server