I assume that you are entering the names into a textbox that is anchored in
the header of the document.  Display the Drawing toolbar via View>Toolbars
and then click on the arrow head on the left hand end of the toolbar to use
the graphics pointer.  That will allow you to select the textbox and when it
is selected if you move the mouse to the center of the bottom edge of the
textbox, the pointer will change to up and down arrows.  If you left click
when those arrows are displayed, you will be able to drag the bottom border
down to increase the height of the textbox.