Originally posted by smaia
How do I challenge a player?

is he/she required to accept the challenge?
Thanks for helping!

You click on challenge player on the ladder board, if one of the players up to 10 places above you free. But as they are all defending you can not challenge at the moment.
Once you challenge the game starts it can not be refused.
If you want a ladder game you could join one of the other ladders as well.