Upload Get GNews from Appearance → Themes → Add New → Upload Theme. Activate it, then upload and activate GNewsCore from Plugins → Add Plugin. Install the child theme only when you plan to customize code. After installation, open Settings → Permalinks and save once, configure menus, logo, homepage and required publisher pages, then verify the site on desktop and mobile.
Documentation
Install Get GNews
Theme, Core plugin and child-theme installation steps.