That's basically as easy as it gets!
There are however a few small differences depending on what question type it is:
Multiple Choice: see image thumbnails
When you add images to the Multiple Choice question, there are miniatures of the images next to the options in the audience's phones. Clicking on those increases the size.
Multiple Choice: choose more than one option
If you allow the audience to vote on more than one option, this is how it's represented in the phone: checkboxes to indicate that the participant can select multiple options. This feature is not supported by Quiz or 'Who will win?' question types.