First, click the link asking you to follow the author on the Giveaway module- this will take you to their page.
On BookBub: The follow button is in the top right of the author's BookBub Page.
On Amazon: The follow button is right under the author's image on his or her page.
On Facebook: Hit the LIKE button on the author's page.
On Twitter: Click the "Follow" button on the right.