I guess you're referring to browser tabs.
You just need to shut down some open tabs. How you do this depends on the browser you have, but assuming it's Chrome, easiest ways is to go to the menu then tap Close all tabs.
If you want to select which tabs to close, at the top of the screen, next to where you can type in the URL is an icon with a couple of overlapping boxes with a number inside. Tap this to see a list of all the tabs you have open. There's a 'x' in the top right corner of each tab. Tap this to close the tabs you no longer need.
