The CE flag is already registered to your Service Account, and that Service Account has PS3 as a playable platform. To play on PC, you just need to get the Windows platform game license by purchasing Windows client - which essentially is 30 days playtime. You don't need CE copy at all. And in future, for PS4, your current PS3 game license will be upgraded to play on PS4 as well. You will also receive new CE items which bundled with PS4 CE.

* Note: You should be able to add the Windows platform from Mogstation, make sure it is added to the same Service Account (that you use for PS3).