Type the text using notepad or text edit.

copy the first chunk of text, select the portion of the QuickTime movie the text is going to cover (select with the pointer on the timeline) and choose Add scaled from the QuickTime pro edit menu.

to adjust text placement, choose get info and choose the text track and the size option. This will let you resize the text box and move it around.

You can also add an image to the movie by creating a movie in Photoshop, saving it as a gif or jpeg, then opening it as an image sequence and doing a add scaled to the movie. Like the text box, you can move it around by choosing the size option in the get info box.