Hi there,
to add screenshots, save the the image to a cloud drive or your WP Media Library or use an image service like imgur and provide us the link.
The Scribe sites homepage is set to display the Latest Posts ( Dashboard > Settings > Reading ),
So it cannot be directly edited like a static page.
But it can be indirectly edited using the GP Elements module:
https://docs.generatepress.com/article/elements-overview/
Elements are found in Appearance > Elements. Or when viewing a page you will see an Admin Bar > Elements Menu listing those active on the page.
The newsletter section is added using a GP Block Element.
Go to Appearance > Elements, and delete the one titled: Email Newsletter Section