Can anyone help me? (CSS Question)

Man Im incredibly bad at coding lmaoooo

Im trying to change my extended / edit your profile bar but it just wont workkkkkk

This is the code Im using to try and change this

.extended {
border: 3px solid #000;
text-align: center;
margin-bottom: 20px;
margin-top: 15px;
background-image:
url(https://i.gifer.com/UxJM.gif); }

If anyone could give me tips on how this is supposed to work Id greatly appreciate it. Im new to all this and just began this page today so Im still learning as I go.

Also the image is where the URL is haha