Using Marquee Template in 7.O

Site URL: https://www.secretariatcenter.org/horses/sua-sorella

I am trying to add a banner/background image to the footer of my template. The image is fine to display across all pages as the footer already does. I found this really neat hack on youtube but when i follow the steps to put it in the CSS coding area in squarespace it doesn't work nor does it work in the code injection or embed code options, Any thoughts? 

.Footer-blocks--top {background-image: url('https://static1.squarespace.com/static/56dcd2e3b09f95353bb68496/t/62cdc052e1ac2e3eb1392604/1657651285358/Make+a+Difference.png');
background-repeat:no-repeat; background-size:cover; width:120%; margin-left: -10%;}

Link to the hack: 

The guide you posted is for the Brine template of familes, Marquee is not a member, it is its own family. Squarespace 7.0 template families are very unique from each other and if code is specific for one template family  it will not work for another. That is why it will not work for you. Becca mentions that at the start of the video. 

There is another issue as well, Marquee is a discontinued template, Squarespace recommends moving to the Brine family, it is very similiar to Marquee with upgraded features and there is a lot of code to make changes to it.