1)You need Es File Explorer.
2)Install any game/application you want from Google Play Store.
3)Open Es File Explorer,press the left button on Android,then Manager.
4)When is open new menu,press App Manager,then choice your game/application,and long press
on the icon for game/application.
5)Again is open the new menu,select Backup,BINGO,apk is in the backups folder on the sdcard.
6)If you wish,you can delete previous installed apk