not working with wordpress ,theme, oxygen

PC custom css didn’t work anything with WordPress oxygen.
Does someone give me advice,please?

I’m beginer and just started to make my blog.

http://jun-yoshida.com/

I would like to remove “more articles” at the bottom.

I taped ” section-title { display:none; } “
after that “save change”
but it didn’t change anything.

I tried a lots of types of css, but nothing was successed.

in my opinion, smg wired…

please, someone give me advise.

https://wordpress.org/plugins/pc-custom-css/