You can also get a RSS plug-in that will give you a widget to place in a sidebar or place the HTML for a button in a text widget if you have a specific image you want to use.
I did look for a plugin but there were so many of them that said they did a whole lot of other things, too, that in my confusion, I didn't get any of them. Instead, I added the feed url to the two upper nav bars on the site and "called it good"!