How can I fix my banner sizing for mobile and desktop compatibility?

[FWA]

I’m having issues with my banner sizes! I have the free version of impulse and I have tried to input different sizes and nothing is working, I want to try and avoid coding cause it’s not my area of expertise. Plus it’s not letting me add copy codes. (Could be doing it wrong) How do I size my banners so it’s mobile / desktop compatible.

[FWA]

Yes