Go to the Sign in page here. Click on the 'Register' link at the bottom of the page.
Create a New Company by filling in your name, company name, company email address and create a password. Click Sign up when you're done.
Check your email for a welcome message with an activation link from email@example.com (you may need to check your spam/clutter folders, depending on your settings).
What should you do now? See our Getting Started help article for Administrators.