Need to learn CSS?
Check out this page:
ihttps://www.w3schools.com/css/tryit.asp? filename=trycss_website_layout_navbar
copy and paste code on the left
click the "RUN" button
See the results on the right
make changes and hit the button again, over and over
Play around with the css and browse the whole site.(there's a Home button, upper left) You are guaranteed to learn some CSS and html and javascript...
They have a lot of info relating to web development.
***I had health issues that wiped some of my memory, so I go there often myself. Gone are the days of bookkeeping and easy website tech. Web development is super hard now, but I keep on keeping on. And I make lots of notes.
Edited to ad:
Use cpanel, scroll to File Manager
public_html/storefront/view/default_html5/stylesheet/style.css
That's where most of your design settings, css is.