Hi mpurse,
I can help you out with this.
WordPress has its own registration system built in, but that can be kinda SPAMY.
If you have Anyone Can Register Setting in WordPress set, then anyone can register by going to this link: (changed to your site)
http://yoursite.com/wp-login.php?action=register
I did a quick search and found different plugins to help secure that process and not get as many spam registrations.
There maybe other plugins both free and premium that enable you to create your own registration process as well.
Does that help?