It's easy to get intimidated by Android, as a lot of its apps and services are designed more for hard-core geeks than the everyday user. And, initially, I was intimidated by Android Injector, a desktop application that allows you to install APK files (Android apps) on your Android phone and Android tablet - until I used it, and realized just how easy it really is. See also: Best Android apps.
To use Android Injector, you need an Android device connected to your PC via USB. You must have USB Debugging mode enabled, and the proper drivers installed. If all of this sounds like Greek to you, don't worry: it's actually quite simple. You can enable USB Debugging in the settings menu of your Android phone, and your phone likely will install the necessary drivers when you connect it to your PC. If you're using an older Android device, you may need to search for the drivers online; the Android developer site is a good resource.
If you'd like a little more hand-holding, help is available for you, too. The developer of Android Injector pointed me to a desktop application called PDANet, which walks you through the process of enabling the right settings and downloading the drivers, painlessly.
With this type of setup required, I expected Android Injector to have an interface that only geeks could love. But I was wrong: the application surprised me with its sleek design. It appears on your desktop in the shape of - and about the same size as--an Android handset. It even has four buttons underneath its virtual screen, just like a real Android phone. These buttons allow you to locate APK files on your PC and transfer them to you phone, as well as offer access to the app's settings menu and give you more information about it.
To use Android Injector, you'll need to download those APK files on your own, from whatever source. APK files are Android applications; you'd use Android Injector to install them if you can't access them via Google Play. This might be because the developer doesn't have them in the store, or because your device is older and the store thinks it's not compatible with the apps available there.
Android Injector lets you browse to APK files on your PC from within the app; alternatively, you can locate them yourself in Windows Explorer and right click to add them to Android Injector. Once you've located them, the name of the file will appear on Android Injector's virtual screen. You then click the green arrow icon and the file is automatically transferred to your connected Android phone. It's that easy.