You can view the navigation menu by clicking the 'burger menu' icon in the top left corner:
The navigation menu in the default AtroCore theme can be found in Administration / User Interface. It allows you to open list views for all entities in the system.
The navigation menu can be configured by your administrator to suit your needs.
Select the Navigation Menu option and add the desired tabs using the Add button. You can also define the order of the tabs by dragging and dropping them into the tab list.
You can also select options for Quick Create List, Favicon and Header Logo. Other options on this page are described in detail in the following paragraphs.