You can sign up for ThriveTracker here:
We have multiple plan options, including our Cloud plans and a Self-Hosted Option. These can be viewed here: http://thrivetracker.com/pricing/
Once you sign up for the Cloud Plan, your account will be immediately created and available for you to login and get started.
For Self-Hosted users, once you have signed up you can download the installation files at https://accounts.thrivetracker.com/thrive/