The text box is probably formatted as "behind text". If the
Drawing toolbar is not currently displayed, then display it by
clicking on View | Toolbars | Drawing. On the Drawing toolbar,
click on the Select Objects tool (it's the big white arrow button
at the left end of the Drawing toolbar), and then click on the
text box to select it. When you're done changing or moving the
text box, click on the Select Objects tool again to turn it off,
or else you won't be able to select text normally.
