Change menu

First of all. Thank you for the beautiful subject, and my thoughts on English. I’m using a translator since I’m from Brazil and I do not speak English.

How do I change the background of the menu links when the mouse passes over them. (Same as your site) I would like to leave the same color as the bar. I am learning to work with css and I can not find the field class.

thank you.

I do not have a website. I’m learning via localhost.