well i don't have windows 7, but it's probably the same way as the one i have.
ok when you go into the titles and credits part, click on whichever one you want, meaning title on selected clip or whatever. anyway after you click that and you type your text in click on the change the title animation and scroll down until you see one that says typewriter. click on that one then go back and do whatever it is you want to the text
hope this helped
Just click captions aww nvm ill just take a screenshot