How can I click on an element that is inside an iframe?

To click on an element that is inside an iframe, you need to click on the checkbox "This element is in a frame?":

Then indicate the CSS selector of this iframe (it could be "#iframe-something" or just "iframe"). If you want to click in an iframe that is inside an iframe, you can separate the CSS selector of the iframe by "||". For example if you want to click on an image "img" that is inside the iframe "#iframe-player" that is inside the iframe "#iframe-div", configure your campaign like this: