Click the ADD TEXT button and click on SIMPLE TEXT. The text editor opens.
Text can be dragged to any position, via the cross-mark in the preview window, or click one of the alignment icons at the top-right of the text compose box.
Make the desired color, outline, shadow, etc. adjustments, then close the text box. The clip will appear under the IMAGES tab in the bin (top-left of the window).
To superimpose the text, place it on a higher track than the underlying video. Higher tracks always take precedence.
For lots of good info, http://nch.invisionzone.com/topic/23872-videopad-tutorials/