add background image to a lightbox form

Site URL: https://www.FiercePassions.com

I want to add an image to my lightbox form.

This is the code that someone gave me

.lightbox-content {
background-image:url(https://static1.squarespace.com/static/5823b7c7f5e2312802b4e80c/t/60a5ad4aa22ee22cf243b5e0/1621470585083/OsunOsogbo_Shrine_Sunset_over_the_Osun_River.jpeg);
}

but nothing is happening

password is "mexico"

50 minutes ago, FiercePassion said:

Site URL: https://www.FiercePassions.com

I want to add an image to my lightbox form.

This is the code that someone gave me

.lightbox-content {
background-image:url(https://static1.squarespace.com/static/5823b7c7f5e2312802b4e80c/t/60a5ad4aa22ee22cf243b5e0/1621470585083/OsunOsogbo_Shrine_Sunset_over_the_Osun_River.jpeg);
}

but nothing is happening

 

password is "mexico"

Where is the lightbox content trigger

On my lightbox form here 

.sqs-modal-lightbox-content .lightbox-background {
    opacity: 0.9;
    background: url(https://images.unsplash.com/photo-1515549832467-8783363e19b6?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=564&q=80);
}

I gave up. Thank you though.