Depending on your screen size (for example if you are using an iPad), the left-hand menu may not be displayed. It is easy to display the menu by clicking on the "hamburger" icon in the upper left-hand corner of the screen.
The menu will now display and you can select items from it.
Once you have selected a menu item, the menu will minimize again and to show the menu again you will need to click on the "hamburger" again.