Header Image Questions

Greetings. I just downloaded your theme, and it looks good for my website so far, but the header image is rather large.  How do I reduce the size of the header image so that it is thinner/ more narrow than what is there so that the posts are closer the top instead of further below? Also, how do I delete the sample images that are there? Also, if I wanted to create a rotating series of header images, hw do I set that up and what is the time length when images would change? Here is my website: https://radiocasbah.com Thank you, Michael