Lots of people pick up tablets and smartphones that don't have the Google Play Store pre-installed on them. Perhaps you've just granted yourself root access and accidentally deleted the Play Store, or flashed a custom ROM and don't want all of Google's apps. Fortunately it's super easy to get Google's app market place running on your device, so you don't have to worry about missing out on all the Play Store has to offer.
The simplest method is one that should already be quite familiar to you if you're an avid follower of AndroidPIT: just install the Play Store APK manually. An APK is the Android version of a exe program on your computer. Instead of downloading an app from the Play Store, you simply load it yourself without the Play Store's help. This is of course very useful when it is the Play Store itself you want to install!
Be aware, though, that if a device didn't come with Google Play Store preinstalled, that means that it isn't certified for Google Play. Therefore, there might be compatibility issues.