How to operate the elemental point on the iframe

Joined in the web page iframe. However, Kantu’s lawlessness and other elements.

What is the question? Maybe you have a link or a screenshot?

First you have to select iframe with selectFrame command

What I have is another plug-in iframe embedded in the webpage, but the elements on the iframe page cannot be read.

How can I read the content of the iframe context and then read its elements