1) Login to the e107 administration area, and then choose the "Custom Menus" option.

2) Input the following information for the new menu.
<iframe frameborder="0" height="150" src="chat/info_embedded.php" style="width: 100%; margin: 0; padding: 0; border: 0; overflow: hidden;" scrolling="no" border="0" allowtransparency="true"></iframe>
You can tweak the height parameter of the <iframe> tag to adjust the height of the userlist.
3) Click "Create Custom Menu"
Now, on the e107 homepage, a new block will appear with the current users in you FlashChat rooms:
