As Ethos 1 is one of our Standard demos it does not count with content.
You will need to use your own pictures. There are plenty of websites which sell stock photos in case you want.
I like Adobe Photo Stock website because it is quite affordable.
Once you have your photos you will created posts and use this photos as featured images.
Those Featured images and post names will show on top of the images.
Once you have done that, you will also want to ensure that the Post Carousel, Post Slider, and Filterable Index are enabled in Customizer. For more information on this, please refer to the Ethos Customizer video available in the Knowledge Base.
Hope it helps