unechienneandalouse

Thanks for the help!

The creator of my theme gave me a code that actually worked:

@media only screen and (min-width: 1170px) {
.single #main.fullwidth .post-entry {
max-width: 800px;
margin-left: auto;
margin-right: auto;
}

.single #main.fullwidth .post-img {
max-width: 800px;
margin-left: auto;
margin-right: auto;
}

.single #main.fullwidth .post {
max-width: 800px;
margin-left: auto;
margin-right: auto;
}
}