CyanogenMod emulation The device is Samsung i9100. I have downloaded the latest AndroidStudio and going to modify
or create an addon for AOSP contact app.

The system itself is present on the website https://download.cyanogenmod.org/?device=i9100

Does anyone know how to go about Cyanogen emulation?

Also, what I am trying to do is explained by me at Modifying android system apps.

Guys, do I really need to emulate CyanogenMod? Or can I just modify "aosp contacts app" 
testing it under any android emulator and then putting my changes into the CyanogenMod package for Samsung i9100?
The Contacts app doesn't require any specialized device features, so you should be able to test your modifications in an AVD created from the images you download via Studio's SDK Manager. These are just basic Android images, not Cyanogen, but if you're not tying into some special feature of Cyanogen or i9100 hardware, then it will be adequate.

Once you get things working in an emulator, connect the i9100 to your development box and test the app for real. You'll need to enable the Developer Options menu and turn USB debugging on before Studio will see that i9100 as a run configuration target.