If you have created a workspace directly from the calendar event they will have received an invitation to access the workspace you have created (option 2). If that is not the case, we got your back.
Option 1: Click on "Members" or "Share"
Type the email address of the team member that you would like to give access to your workspace and send the invite.
Option 2: Go to Agenda Settings --> Members --> Invite Team members
💡PRO TIP: How to remove a member from a workspace