You may enter text as
you would in any word processor. Use RETURN
to start a new line, if necessary, and click on the button in the
toolbar that says "Text". Then type some text --
your name, for example. Notice that the characters are a different
font, and the dotted box and underscore are gone. This is a text line.
If you press RETURN, you obtain another text line. Type text on this
line
as well.
Now, click on the button in the toolbar that says "Math". Type
5.3*7.1 and then RETURN. You're back to math input.