You can participate by doing one of the following three things (or all three):
Choose someone on your friends list and:
1) Leave them a comment telling them how much you appreciate them.
2) Read one of their stories you've never read before or look at a fanart or a video they made and give them feedback.
3) Write something or create something for them.
Or find another way to appreciate them.
You can find more information in her post here.