Gillion theme has three predefined widget locations where you can place your widgets.
To access widgets go to Appearance > Widgets. From there you can add widgets by clicking on them and choosing the right location.

Here is the full list of available widget areas:

• Blog Widgets – for blog pages and blog posts
• Page Widgets – for standard pages
• Page Builder Widgets – for pages built with page builders
• 404 Widgets – for 404 pages
• Header Side Menu Widgets – for side menu header
• Shop Widgets – for WooCommerce pages
• Footer 1,2,3 Widgets – for footer