Is it possible to create a gallery of POSTS, not of post categories?

HELLO, I see that "Content Source" has: (Post Categories, Pages, Tags, and Custom Post Type)...

What I want is to create a gallery of POSTS not of post categories... What I want is this: (https://www.truevalhalla.com/)

note that those are POSTS, not post categories.

Is that possible, if so how? as I don't see that in the options.

Thanks!