You can create a ProductPlan account by clicking the Sign-Up tab. Getting started with a Free Trial is easy and does not require a credit card. You can choose to sign up with an existing Google account or create an account with the email address and password of your choosing.
Once you've signed up for a Trial, you can invite your Team to try ProductPlan as well. Simply enter their emails in your Users page and start collaborating on your Roadmaps.
New users joining their Team should not create their own independent account! As stated above, you will always invite them to join your Team.