To access the debugging tools, you need to click the sixth icon on the left-hand side panel icon bar, which usually shows a Show the Debug Navigator tool tip, and this will give you direct access to the debugging tools.

Understand that accessing this panel without running a game on the device will show you a totally empty panel. You must have a running game on the device to start seeing the tools shown here:

The first part called UE4Game has general information about the game. It is not much, but it is useful anyway. It gives you the PID value, which is the process ID of 601, and the current state of this process, which is obviously Running.

The second row of the toolset is the CPU. Accessing it will show you how many threads the device is running at the moment, the performance of each thread, and the utilization of each running process. Because you are running UE4Game, it will be the main focus here; any other running processes on the device will be listed in Other Processes...