Any organisation can use HalSail. You might be a sailing club, or a yacht club, or a regatta authority, or a general watersports club, or a youth organisation, or anybody that runs sailing races.
Each organisation can register any number of people to use its account. When you agree our terms and conditions and click Register you will become the person with permission to add other people to use your account. Note that this is not the page to set up a new user of an existing account. To do that, log in as an administrator of the existing account and add a user from the Admin menu.
If you are familiar with Hal's Race Results on a Windows computer you will be able to get to grips with HalSail very easily. If you are not and want to play with some fictitious data in order to understand how the application works, go to the tutorial in the Help menu after registering and load the demo data.