Shopify Supply Theme slideshow doesn't work with the usual code

[UFG]

I'm new. I'm interested in know more about coding.
Supply Theme sliders do not occupy the end-to-end sides of the webpage. About 25% of the home page on the side is made of white space.

Two experts sent me the commonly used code, however, doesn't work on my site.

.lazyload__image-wrapper{
max-width: 100% !important;
}
.template-index .main-content {
padding-top: 0px;
}