How to remove or sidebar from theme?

Hello

I want to remove the article tab or sidebar from several pages within use of this theme on my site.

I have downloaded a custom css plugin.

But upon inspection of element i have not seen exaclty how i can remove the sidebar?

Please can you help?

Please assist by letting me know how can i remove the sidebar?

If i use custom css with the important! and display none attributes then what would i use to label the style properly?

I look forward to your help.