Steps to apply the code.
1. Go to Weebly > Design > click on the "Edit CSS/HTML" on the bottom left.
2. Click on the "main-style.css" on the upper left side.
3. You will see sets of codes on the right panel. Scroll it till the very bottom.
4. Paste the following in a new line at the bottom of the page:
If you completely want to remove the sidebar, simply paste the code below at the bottom of the page.
display: none !important;
Please note that you can change the margins, padding, width depending on your website settings