Is it possible to share the URL of your application under test? This would be the easiest way to assist you.
Otherwise, I’d have to guess what your problem is all about since elements inside of iframes can be accessed by using selecting the frame right before via the selectFrame command. This command uses Frame Locators to identify the frame in question.
The most easiest way is to simply record your interaction as the necessary selectFrame commands are automatically inserted then.
Hope that helps. Otherwise, please describe your problem as detailed as possible.