You press the home button to exit an app on an iOS device.
Except in the case of a navigation app, that usually leaves any active route running in the background.
I only have it installed on my iPhone, so my instructions may be a bit off.
On the main screen (when navigating) there should be button with 6x blue squares in it. Tap this and look for a Clear Destination option. On the iPhone it's smallest icon at the bottom left. If you don't see it there tap the Main Menu button, then the Routes tab at the bottom. There should be a Clear Destination option in the menu.
Once the app is not longer in navigation mode you can close it as normal (with the Home Button). It will no longer be active in the background.
Failing that, you can force the app closed (cleared from RAM).
Close the app using the Home Button. Double tap the home button. The multitask bar should appear at the bottom. Tap and hold on the app in the list until it starts to jiggle, then tap the minus sign that appears at the top left corner of the icon. This forces the app from memory, and all background tasks will be terminated as a result.
Hold in mind that apps that appear in the multitask bar may or may not be running, depending on whether they have active background tasks (most don't), and may or may not be in RAM, depending on whether iOS has purged them automatically in order to free up RAM for newer apps. The list indicates nothing except what apps were running at one time, most recent first, though the most recent ones are probably still in RAM.
Apps in RAM but not running in the background (music, navigation, and a few other services) do not normally affect CPU or battery performance. There are exception, which is why if you are having problems it's not a bad idea to clear them manually as described above; or restart the iPad which will also clear them, but leaves the list intact.
Ok, overkill, but I was trying to anticipate the next question(s).
