While the Facebook installation instructions touch on this, to get this to work you need to do a little extra work.
In each of the apps there's a file called "config.php". You have to edit this or it'll always show as Arrowchat in both the Facebook and Twitter.
For Facebook you'll need not only the name of your fan page but the number of the page. You can get this number by going to your Wall Page and looking in the url bar. It's a big number (12+ digits) so you can't miss it.
For Twitter all you'll need is your Twitter name.
Not sure why this was all left out of the installation instructions, but there you have it. They are both great apps so enjoy!