In the upper right-hand corner, look for a box that says, "Type a question
for help".
In that box, type SIGNATURE, then hit "Enter"
Follow the instructions for "Create a Signature for Messages". Depending on
whether you use plain text, HTML, or Rich Text, you may be able to create a
letterhead in color, different fonts, etc. Don't go crazy here; folks with
PDA's and cell phones don't want to have your messages cluttered with crap.
You might also want to look at "Stationery" under Help. But I agree with
the other poster. Keep it simple. Too much is too much and makes your
messages hard to read and slow to download.