If you have more than one player on your computer, I have found that I have to reload every time I want to use it. I reload from the Profile, then Achievements page. It's near the bottom.
Then back out of all facebook and MW tabs and pages. I use Firefox. It does not seem to work if you have a Live Feed with a special list set up running, thus back out.
Click on Facebook on the tool bar and it will open the News feed page of Facebook. Then click on the Play Now on the Tool Bar and it should give you the 25% bonus.
Sometime the bonus is Energy sometimes it's Stamina.