Step 1 – Install/Activate Free Plug-In
Install and activate the plug-in: RSS Icon Widget 2.2.
Step 2 – Go to Appearance, then Widgets, Drag Widget to Sidebar
In your “Appearance/Widgets”, drag the “RSS Icon” to the sidebar.
Step 3 – Change size, click “Save”
Set the size, I prefer 24×24 or 32×32. Most people are used to the orange color (as you see on the right side bar of this page), so I suggest just accepting the default color.
On some blogs, either the widget is hard to find, or people do a CNTL-F (Find) for the phrase “RSS”. So to the right of the icon, the default text is “Subscribe via RSS”. You can change it, but regardless of what you might change it to, I strongly suggest you leave the phrase “RSS” in it.
The widget will automatically have the correct link to the RSS page of your WordPress site, regardless of which format is being used.
So Install, Activate, Add Widget, Click 24×24, then Save and have fun.