Creating a contest was described in tutorial, however example is the best to learn from.

Creating a simple contest

Admin - setup

/ca start mycontest
/ca mod mycontest banned add EvilGriefer854

User - joining

/ca list
/ca info mycontest

NOTE: /ca list and /ca info mycontest are not neccessary to join the contest, but it's worth checking that not to break rules. (few days of building) (stands in front of it)

/ca sub mycontest

(visits friend's entry)

/ca tp mycontest

Admin - closing contest

/ca stop mycontest

Few times in row:

/ca tpord mycontest

TIP: Use UP arrow on your keyboard to type the same message next time. After a lot of hours of judging:

/ca win mycontest Notch

Creating an advanced contest

(waiting for developer to add description and rules editing option - wait I'm the developer :D )