The Area Code Games event is a week long tournament played at Long Beach State in late July.
The actual games are an invitation-only event, and scouts from various MLB clubs make the selections based on invitation-only tryouts. There are eight teams representing different regions of the country. From Wisconsin, you would probably be trying out for the White Sox team.
Tryouts and camps are different things. You can attend an Area Code Camp, times and locations of which are posted, and compete well enough there to be invited to the tryout, which is usually the following day. A lot of the players invited to tryout are already known to local scouts, and did not participate in the camp to get their invitations.
These camps are also good low cost alternatives to getting basic data about your velocity, running times, etc. They usually do SPARQ testing there too. It costs around $100 versus $500 or more from some showcases, although in the showcases you will get a greater opportunity to actually play some games.
All the basic information you need is at this link:
http://myespn.go.com/blogs/highschoolbaseball?tag=area%20code%20baseballYou need to fill out an online profile. Also, there are fliers on currently scheduled camps.