Once you've upgraded to the Team plan, you'll be sent through a small series of overlays to help you get your team up and running. If you opted to skip that initial set up or would like to add users anytime after, you can invite teammates to join by clicking on the Team settings icon in the left hand sidebar.
In the resulting overlay you can edit your team name, invite users, and edit teammate roles. To send an invitation, enter your teammates email address into the text box and click the Send invitation button.
Great! Your teammate will be sent an email with a link for them to join your team. If they don't have a Boords account yet, they'll be asked to sign up before joining the team.