How to install cyanogenmod on LG P690 optimus net: how to know which ROM?
The YouTube video refers to an XDA page as shown below:

That XDA page gives further details about the CM9 ROM, GApps and instructions.

Your LG P690's hardware seems to be a close match to my LG P500. So, if you are not satisfied with the ROM mentioned, you can give a shot with LGP500's ROM - the chances of getting it working in your P690 is good. Please search this site for details on knowing from where to download ROM for P500.