In the upper left corner of the page, you can find the navigation icon which opens the navigation drawer with available destination pages.

The opened navigation drawer with currently available items.

At the top of every page, there is always a breadcrumb-style navigator, so you can always tell where in the application you are. For example:

You can backtrack by clicking on the "Libray" text (breadcrumb item), and you can always go to your defined start page by clicking on the icon in the shape of a house.