You should be presented with a list of apps.Scroll down and look for install from unknown apps.Find the Security & privacy option and tap on it.While there could be some slight variation in exactly where you'll find this setting on your Android phone, it's usually buried within the Security & privacy or App menus. Most Android skins will present you with a shortcut to this page when you try to get the process done alongside a series of warnings. If you have tried to sideload an app before then you will be familiar with this menu. How to set up your device for sideloading.
