Simple Read Header.

Hello,
So…where to start, I have been going off 8 themes trying to figure what and how to add it. I finally found a theme that is both masonry layout and parallax header or a header slider(Simple Read). But now I can’t change the header from latest post to just pictures I want feature(like a gallery, an example would be the byblos theme.) Can Anyone help me so I can stop ripping out my hair. Also if you need the link to my website it’s supersophistakit.com. I look forward to anyone’s help and will thank you in advance. (Also, how do I center the Site title and tag line?)