You can enlarge the "tiny" space by dragging the textbox higher (or lower).
Make sure you have correctly followed the instructions and registered the DLL that you've found here:
http://www.mongfish.com/msnmsgr/
Also, you don't use the send button when you use the convert function. You write text (with your mous) in the convert tab and it will be automatically converted to typed text in the lower box.