where do i put this code?

im using the following code to have a fixed position picture w/ link on the right side of my blog content, i know i need to put the CSS in styles.css but where do i put the div content

#fixsidejoin {
width: 15%;
height: 15%;
position: fixed;
bottom: 300px;
left: 970px;
color: #cc0000;
border-top: 0px;
border-left: 0px;
border-right: 0px;
-moz-border-radius-topleft: 7px;
-moz-border-radius-topright: 7px;
margin-bottom:-30px;
}

<div id="fixsidejoin">FIXED POSTIION</div>

id like this to show up on every page/ individual post.. etc
thanks !!