I can´t change CSS

Hi, good afternoon
I’ve installed this plug-in because i want to show the social icons in the menu bottom, but they still showing vertically (because ther’s no way to put they in only one
“li”)
by the way, i’ve tried to change my css and still not working, i don’t know how can i adjust it.
What i want to do is putting they in a single line, but maintain their links.
I hope a lot that someone could help me,
so, accept my best regards and thanks a lot
https://ww.wp.xz.cn/plugins/menu-social-icons/