Hi,
Have you read the documentation on creating a registration agreement? http://www.mojoportal.com/creatingaregistrationagreement.aspx.
If you create the agreement, it will show up on the registration page. You will not have a checkbox for accepting but you could include text in your agreement that stating, "By clicking the 'Create Account' button you agree to these terms..." or something like that.
HTH,
Joe D.