ESSBEEAY – if you’d like to remove the sidebar on certain static pages only, then Cecilia’s suggestion above is a good one.
The best way to make changes to a theme is to use a child theme, so any tweaks will be overwritten and lost every time you update the theme. Here are some guides in case you haven’t made one before:
https://codex.www.ads-software.com/Child_Themes
https://www.smashingmagazine.com/2016/01/create-customize-wordpress-child-theme/
https://op111.net/53/
https://vimeo.com/39023468
Keeping your theme up-to-date is important so you’ll get all the latest bug and security fixes, as well as keep the theme compatible with the latest version of WordPress core.
Here is the Codex guide on creating a page template:
https://developer.www.ads-software.com/themes/template-files-section/page-template-files/page-templates/
You’ll need to remove any call to the sidebar in your new page template and add CSS to expand the width of the main column so it fills the entire width of the page.
If you want a full-width page anywhere other than static pages (i.e. particular posts, blog page, etc.) then you can accomplish that with custom CSS alone, and you don’t need a child theme – you can use a custom CSS plugin like the CSS Editor module in Jetpack or a standalone CSS plugin.
If you need help going either route, let us know.