"If your chat box is visible, try left clicking on the wide gold band at the top of the chat box. Hold it down and you should be able to drag the box around to where you want it. You can make it larger or smaller by left clicking on the bottom right of the box where it looks like a square over another square. Just click and hold and drag left or right and up or down. Just do the top band first so you have room for expansion. Good luck. "
Next, this method involves deleting a file on your computer that will reload the next time you launch Wizard101:
"In case anyone else has the same issue, I've found a much better fix to this problem; that does not involve reinstalling wizard101. This is a fix for Windows, if you have a Mac, the steps may be slightly different. Firstly, you will want to close the Wizard101 client. Right-click the Wizard101 shortcut on your desktop and select "Open file location." Your address bar should be as follows:
This PC > "Name of your hard drive" > Programdata > Kingsisle Entertainment > Wizard101
Double-click on the "Bin" folder, then locate the "Config" XML file, located within the "Bin" folder. Delete this file. Reopen the wizard101 client and log in to the game and go on to any of your characters. The chat box should no longer be stuck in the bottom right corner."
Some players have just reinstalled the entire game.
Finally, if none of these help, contacting Support for more assistance: