Initially, the helpdesk system is set up with one user account. The Root user. This user is not a normal member of society, in that they have no access to submit issues or view existing issues. Root's sole goal in life is to set up the parameters for the system. The initial username and password are root and root. As administration is cascading, the least amount of work the Root user must do to get a fully working system is to do the following:
Create a new domain (or modify the "demo" domain that is initially present in the system) to use as your helpdesk's domain. (see Working with Domains).
Create the first (and maybe only) site for that domain. (see Working with Sites).
Create a user account for whoever is to take responsibility for the administration of that domain and give them "Domain Administrator" access to the newly added site. This new user will then take over the job of setting up that domain correctly. (see Working with Users).
For an average implementation, you should be looking to have at least two priorities ("Low" and "High") and two statuses ("Open" and "Closed"). For larger implementations, more would be prudent. Examples of a few different implementations can be found in the chapter Implementation Examples.