Reduce Banner on Mojave Template to remove white space

Site URL: https://morrislabel.squarespace.com/about-us

Tried and true question - I know.

I am trying to reduce the white space between the navigation bar at the top of the site and the slideshow gallery directly below (refer to example image attached). However , the gallery appears to be positioned on a banner and (I'm guessing) the banner needs to be reduced to move the gallery content up into correct position.

I have seen code like below - a fix for the Bedford template banner 'padding':

".transparent-header.view-list .banner-thumbnail-wrapper,
.transparent-header.collection-type-page .banner-thumbnail-wrapper{
   padding: 180px 0 155px;
}"

however when applied to the Mojave site, through the code injection on the Advanced tab of the Banner Editing option of the page, it doesn't appear to change anything.

Is this a case of not applying the code correctly (to the correct lines)? Will this code work for Mojave? Or will the code only work when the website is published publicly?

Any solutions to this head scratcher are welcomed!

Hi. What is access password?