reduce padding in article

I would like to reduce the side spaces and I tried to change the rem as in the attachment in custom css but nothing changes. Where am I wrong?

Your custom code lacks of curly brackets {}, I updated for you and it's working now:

@media (min-width: 992px){
.single-blogs {
    padding-left: 4rem!important;
    padding-right: 4rem!important;
}
}

thank you