Newbie – navigation bar listing problem

Firstly, thanks for a great theme that’s easy to use for brand new newbies like me! But I have a problem with the navigation bar – every time I add a new page, it lists it in navigation bar alphabetically – ie: Bio; Books; Contact us; Essays; Home. But I’d like to decide how they are listed – eg: Home; Books; Essays; Bio; Contact Us. Is there a way to do this? Please explain very simply and in detail – I’m totally new at this. Thank you!