To change the order in which your tabs appear, drag an object using the three lines to the left of the object and move it to the where you want it in the order.

To add additional objects to your navigation bar, click "Add More Items"

Under the "All" tab, you can browse available objects or search for one specifically in the search bar at the top of the window. Click the "+" next to an object to add it to your navigation bar. Once you've selected the objects you want, click Add at the bottom right of the screen.

Some tabs are always in your navigation bar by default and those cannot be removed.

For any tabs that you add and later want to get rid of, click the "x" to the right of the object name to remove it from your navigation bar.