1) Using your GeekLog administrator login, click on Blocks to create the Who's Chatting list:

2) Click on the New Block link:

3) Fill the form with the following information (if a field isn't mentioned, leave as it is), then click Save. If you uploaded the FlashChat files to a location other than the "chat" folder, then you may need to chage the src=".." path below.
<iframe height="150" frameborder="0" 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.
4) Go the the home page of your GeekLog site. You should see a new block:
