1. Go to SDK folder
Go to android sdk folder in which "android.bat" and "emulator.exe" are located.
ex) Default folder on Windows: C:\Users\{user}\AppData\Local\Android\sdk\tools
2. Run AVD manager
Type in "android avd" in the command prompt to launch the Android Virtual Devices manager.
3. Create AVD
Create a AVD by clicking "Create..." button.
Or you can just use the one already created from the list.
4. Launch emulator
Run the AVD either by using command "emulator -avd <name>" or by clicking "Start..." button on the AVD manager.