Running the Android Virtual Device Emulator:
Open Eclipse and load up your recent android project. (If you don't know how to or what is eclipse, read This)
Now goto Run > Run Configurations
And select the 'Target' tab right beside the 'Android' tab and open the AVD Manager.
Select 'Device Definitions' tab and select a device according to your PC/MAC specifications, ( If you select a more powerful or higher resolution device than your screen resolution, the emulator might crash ) then click 'Create AVD', and click OK on the next screen.
In your 'Android Virtual Devices' tab a new device will be create. Select your device and Click on 'Start' and then 'Launch' and your virtual device will be launched.
Making an App and Testing it:
Minimize your Android Virtual Device and Close AVD Manager and Run Configurations.
Select your project from the projects tab and select 'main_activity.xml' and switch to 'Graphical Layout'.
Now add anything you like to your app, like a button or maybe some text.
Now make sure you have your Project name selected on the left and click on the small play button > Run as > Android Application.
In a moment or it might take a minute or two (depending on your PC/MAC speed) your First Android App will be live on your Android Virtual Device.
I recommend you to play around with it, add buttons, add swipes, add your own text. You will learn a lot of stuff!
If you have any question or anything, Please let me know down below.