Here is a little "tutorial" of how to use tourney posts.

To be honnest, tourneys posts are likely the same than news posts, except for the ability to define a time period for the event.

The time period must be in the right format, as given by the default text.
Format is YYYY/MM/DD@HH:MM.
Year must be with 4 digits, all the other ones, 2 digits.

The most important, in my opinion, are the features available for the creation of your posts. BBCode has been especially designed in order to allow tourneys posts to be quite standalone. It means that in a single URL, you will gather all the needed for the tourney.