Mobile Menu & Style

Hi all. Sorry, the site is not yet live so unsure if I’m asking this a little too early.

I’m just on my first attempt at building a site with FSE using Twenty Twenty-Four.

I’ve achieved everything I wanted to other than the mobile menu. I’ve created a separate nav but how do I then assign this to the mobile menu?

Also how do I style it? It’s currently showing a pure white background with the main desktop nav all to the right with zero padding. Screenshot can be viewed here.

Any help would be much appreciated.

Thank you.

Mike.