WordPress.com has several Twitter integration options (Publicize to Twitter, Embed a Tweet, Add a Twitter Timeline Widget, Add a Twitter Sharing Button, Add a Twitter Follow Button) . See here http://en.support.wordpress.com/twitter/
I have gone over the sharing page very carefully. I am sure it is correctly filled out. After saving, it says at the top “Settings saved,” but still the icons are not showing on the blog. I am trying to see them in Safari.