CSS grids can be an easy way to incorporate a grid system in to your web designs. Below is an example of a responsive 12 column grid, divided in a number of ways.
First, add your generated CSS code in to the CSS section of your site.
Each blue rectangle below is a row. You can make any html element a row by setting it's class to 'row'.
Add elements inside of your row with a class following this format: 'col-#', where '#'' is equal to the number of columns the element should span.
The featured code section shows how to set up the first row below.
<div class="row"><div class="col-4"></div><div class="col-4"></div><div class="col-4"></div></div>