To add a button to Announcement Bar, like this.
You can also use this tool to add announcement bar, so you won’t need to use code to add button.
#1. First, highlight text > Click Link icon
#2. Enter desired url
#3. Use this code to Custom CSS
div#announcement-bar-text-inner-id p a {
text-decoration: none !important;
background-color: red;
padding: 5px 10px;
border-radius: 5px;
display: inline-block;
}