How to influence the styles of the YouTube player hosted on your site through your styles?

Question

WordPress

I can’t find/set the path in the styles for the player to set my style parameters through the styles of my site (I don’t forget about !important)
I try to include the player in my block, but the styles do not change
The player is added by the Featured Video Plus plugin https://ru .wordpress.org/plugins/featured-video-plus/
I'm doing something wrong, but I don't understand what )
Here cg91812-wordpress-3.tw1.ru
player
Help, who than can)

Answer 1

add in css

.fluid-width-video-wrapper iframe{border-radius: 10px;}