Checking Responsive Design


I am new to visual composer.

I am trying to control how the different responsive designs of my website and I’d like to eliminate the header pics for the mobile version.

I have watched this video from library, but I don’t have the option shown in there to choose the different screen sizes:

Can you help? Do I need to activate something I don’t know about?

Also, how can I eliminate different elements for the mobile version?

I have watched several videos from the library, but they only play music and don’t explain anything, and then they show something about offset and columns but not how to eliminate elements for the different screen sizes.