You'll know if it's working if you see a bright red heart on a published post.
If it's not appearing for you, here's what you must do to enable it:
Go to your "User Profile" and select "Edit Profile."
In the next window, uncheck the box at the bottom:
Go to any forum post, and the "like" button (a red heart) will be visible.
If I ever figure out how to make this appear automatically, I'll make note of it in this post and mark it as "solved."
