Go to Setup > App Settings > App Designer
This feature allows you to change the order of the items that appear in the main menu within the app. To change the order, simply hover over the menu item you would like to move, and drag it to the desired location on the list.
Please note, the first item on the list is what users will see when they log in to the event.
When you are happy with your changes, click on Save Changes at the bottom of the screen.