Borrowed titles will automatically begin downloading in the background, assuming you're connected to the Internet, and downloading is supported by your device and settings. 

A progress bar shows along the bottom of the reader, and controls are displayed above the text. Tap once in the center of the screen to hide the progress bar. Tap again to bring it back. To begin reading, tap or swipe on the right-hand side of the screen to move forward. 

And on the left -hand side of the screen to go back. Tap Close in the upper left-hand corner when you're done reading. Return to your most recently opened title by tapping on the orb at the bottom of the screen. 

The orb will fill in with the jacket cover of the title you last opened.