Unable to Edit Theme

I am currently using my desktop instead of my laptop, and it is working for now.

I do have some additional questions.

1. I am unable to edit the header image on pages other than the home page. When I go to edit the new pages, it has the tiger and the page title. I have tried editing the featured image, but that shows below the tiger and the title that is at the top of the screen. I have looked through the theme instructions as well as the FAQ on the Catch Themes page. The theme instructions for headers work, but when I add a header to the page, it still has the original tiger image with the page title and then the new header below it. When I follow the FAQ instructions, and go through appearance–>themes–>etc. there is no option for modifying the header or selecting which pages it is visible on. I am not sure what else to try.
2. When adding blocks that have a black background, how can I eliminate the white spacing between the blocks?
3. Is there any way to add images to the backgrounds of blocks? A lot of the blocks I am using have white backgrounds, and I’d like to break up the blocks with a textured background that I have used as the header of the home page.

Thanks so much for the response, but unfortunately, it hasn’t helped.

When I get to the list of templates, I do not see any of the pages I created. I do however see the page template types and I selected “blank” as that is the type of page that I added. There are no options. It is a blank, white page with the following text “This is the post content block, it will display all the blocks in any single post or page. That might be a simple arrangement like consecutive paragraphs in a blog post, or a more elaborate composition that includes image galleries, videos, tables, columns, and any other block types. If there are any custom post types registered at your site, the post content block can display the contents of those entries as well.”