How To Replace Serious Slider Demo Images With My Own Images

My “Serious Slider” headlines, sub-heads, and buttons are the way I want them for the three sliding headers, but I don’t know how to replace your demo slider images with my own images. I thought I could work directly in the html code by replacing your demo images (for example “http://demos.cryoutcreations.eu/wp/fluida/wp-content/uploads/sites/6/2017/12/slider-demo02.jpg”) with the url of an image in my WordPress media library (for example “https://www.fletchergroup.org/wp-content/uploads/2019/03/HOMELESS-BOY-GRAY-WALL.jpg”). That does manage to replace the image, but the sliders then stop moving.

I fooled around in the Serious Slider interface, but could not figure out the relationship between “slides” and “sliders” and how to make them work. Can you please advise me?

Thanks!
Richard

Two other little things:
1) The sliders were sliding every three seconds or so previously, but seem now to have stopped. Where is their timing and movement controlled?
2) A blue “house” icon linking to the Home Page appears on a gray horizontal bar at the top of the page between the sliders and our company name. How can this be removed?

Many, many thanks!

Website: www.fletchergroup.org/building-recovery-ecosystems