SEO for dummies?

Hello.. I’ve been trying to get my tiny mind around making SEO happen on my site https://www.apetronic.com and I’m not really getting it. I’ve installed the Yoast plugin and it appears to be working.. I guess. When I look at the SEO status thing (little red dots next to my posts) it seems to be indicating that it’s not rating well at all. I haven’t ticked title settings within the host settings as I’m scaresd that I’ll break it.. in fact, I have zero, followed by many other zero clues as to what I’m doing in there. Would anyone be able to point me towards some sort of SEO for dummies thing on youtube.. or maybe look at my site and let me know if that’s possible, and maybe determine what I can do.. I really am mentally deficient in the world of SEO (amongst many other areas).

Thanks