Hi Genevieve,
Do you have the Flash software? They have some great tutorials available to help you do many different things.
Otherwise, there is a site called
FreeFlashHeader.com that might help [I haven't used it so don't know how flexible it is, but might be worth a look]. Here's
a tutorial I found that explains how to make a header using the website - but check out the main website, it looks like they have up to 50 templates for free users, so maybe there's one that will match your vision.
I hope that helps!