To access the Battles page, the first step is to click on Battles in the left side menu:

You will be presented with the My Battles page, you will access the list of all your active battles:

You can view the details of an active battle by clicking on the corresponding tile:

There are several things that you can do on this page: 

To access the overview of all the battles, click the All battles button in the top navigation bar:

You will access the list of all the active battles within your company:

You can view the details of an active battle by clicking on the corresponding tile:

You can also access the battles which have been completed in your company by clicking the Battle history button in the top left corner:

To access the Leaderboard, click the Leaderboard button in the top navigation bar: