If you just want to make it “Karaoke-like”, then just use the text generator, and in the text generator select center-bottom as the position.
1) Add a new video track above your background video.
2) Insert markers at the beginning and end of the region where you want the text to appear.
3) double-click on the new video track between the markers to create a region. when you insert Generated Media here it will take the region length as the generated event length).
4) Right click on the new track in that region, then click on “Generated Media”, select “Text Media”, then type your text.
Keep in mind that I am not in front of my Vegas computer and I rarely use Generated Media (preferring to use Photoshop), so this is all from memory. But it should steer you in the right direction.
Steve Mann
MannMade Digital Video
http://www.mmdv.com