Call The ValidEmail() Function In The SubmitIt() Function?

I'm in the middle of a JavaScript class, and I've run into a problem with one assignment. ^^; I've been given a pre-written script and HTML code to work with, and am required to modify it. Here's one thing I have to do, via my instructor:

Add an "email" field to this form. This field should also validate as a valid email address. (Hint: after adding the form field to the form itself, your next step will be to expand the function named submitIt() by adding a second if statement to confirm the contents of the email field. You will want to paste into the header and use the validEmail() function which you will find in Script 7.15, highlighted in red on pages 192-3 of your textbook.)

I know how to write the code to validate an email address, but I can't figure out how to call the validEmail() function in the submitIt() function. The code I have now just blanks out all the fields when I hit "submit." Here's the part of the script with the email validation:

window.onload = loadDoc;
function loadDoc() {
resetForm(document.forms[0]);

[code].....