Actually, installing WordPress these days is super easy. Most hosting providers with cPanel included have automatic installation scripts; installation manually is even easy. However, installing WordPress locally might be a bit tougher, but even that isn’t really difficult.
I would agree, however, that trying to code WordPress themes from scratch, would be probably more than you might want to take on if you haven’t a solid foundation in HTML/CSS and PHP. I would definitely recommend picking up the basics, and even design really, before more complex languages.
Once you’re ready to tackle WordPress, you might try a guide like How To Become A Top WordPress Developer.