Yes, you have to associate your google adsense account with IRC. It is not associated automatically. As you said you already have adsense account from ISC, so you can associate your existing account now. Gold level is required for only new application not for existing one. So friend, what are you waiting for just click on adsense revenue in your profile at the left top of this page and associate you existing account. Hope this will help you.
With best regards,
Working for an ideal and peaceful society.