How to get in a challenge

I would like to join a challenge but they all seem closed. How do I get into one that is open? And what are these games?

how about starting your own challenge?  I'll join, just let me know!  But the challenges are limited because because small groups are more successful, so you might want to limit your own challenge to a dozen people. 

How about a power week challenge... see who can lose the most?

Sure I'll start one, what's a power week?

I too would like to join a challenge. So far I've lost 85 pounds and have 25 to go... I need a BOOST !