Center edit boxes (home, news etc..) NOT the nav buttons

I’m trying to get the text boxes to center with the rest of the page, but the text box just aligns to the left. I’ve tried custom code..

The only thing that has seemed to work, is when i went into the inspect element and did width:inherit;

.content-page{
text-align:center;
}

.site-content{
text-align:center;
}

.content-page{
float:right;
}

.site-content{
float:right;
}

Nothing seems to work.