I should say first that I am not an expert on the blitz games, but here are some 'educated' guesses from me.
The games are unrated at this time.
Yes, you must play rather quickly.
There are a variety of time controls that you can select when you are the one who sets up a game. This is done at the bottom of the page using the option boxes you will see there. Once you have posted a game you have to wait for someone to accept it.
If you choose to play one of the games being offered you accept the time control offered by the opponent who put the game up.
You can watch other players as they play by clicking on their username in the column on the right side of the page. This will take you to their game and you can observe.
I hope this helps, and perhaps someone more experienced with blitz can offer more advice!