How to add background colour to a Secondary navigation on 7.0

Site URL: https://sophisticated-cloud-florence.squarespace.com/?password=demo

Hello there, 

I'd like to add a black background to my secondary navigation where my CONTACT link is.

Can anybody advise on how to do this please?

Link is https://sophisticated-cloud-florence.squarespace.com/?password=demo

Thank you

Claudia

Add to Design > Custom CSS

nav.Header-nav.Header-nav--secondary a {
    background-color: black;
    padding: 10px !important;
}

Amazing! Thank you 😃