Page template width

Hi, I want to create a page template that does not have a sidebar.
I created a new template called bio.php, where I removed where it calls the sidebar and added this above the header:
<?php
/*
Template Name: Bio
*/
?>

This removed the content in the sidebar, but the divider was still there and the width of the content remained the same.

In a tutorial on the web they recommended to “You’ll probably also want to find your content div and manually add a width style to it to extend the width to fill the entire container.”

My question is how do you do this (and remove the divider) ?

Thanks,

KM