There are several different kinds of tabs in Audio Notetaker; the Home Tab a Project tab, and various file managertabs. When you first start Audio Notetaker you will see the Home Tab, to open a Project tab either click on one of the HomeTab options or click the '+' icon in the tab bar. The file manager tabs can be opened from the Home Tab or from the App Menu (the green button in the top left) and Manage.
All the functionality of Audio Notetaker can be accessed through the various tabs and their toolbars.