A Club Ladder is a ranking of players not on their assigned ranking but rather on their record with other players. When you beat someone ranked higher on the ladder you take their position and they drop down one spot.
To challenge someone in the ladder click on the little green symbol 
. This will bring up a page where you can send the person a short message. Click
Send Message and you are on your way. A challenge match itself is a best of five set using English scoring to 11. When the match is complete, record the result in the Recent Challenge Matches section.
You may notice a little lock symbols 
next to names in the ladder. This indicates that the player is currently in a challenge match, which means that they have to report the score of their challenge match before they can be challenged or challenge someone else.
If you have any questions (or suggestions) on how the ladder works feel free to drop us a line: support@sportsynergy.net