By default, the owner, an admin, or a manager can add users to a team; however, there's also an option, in the team sharing settings, to let anyone with the team member role invite users. You can also control access by assigning roles to your users.
To add users to your Enterprise team:
Sign in to your InVision Enterprise here: your-team-name.invisionapp.com
In the lower-left corner, click the [Your Team Name] dropdown, and then click People & Team settings.
The Team page will open with the People tab active.
Click the + sign at the top right.
Enter the invitees’ email addresses, separated by commas, and click Next.
Verify that the email addresses are accurate, make any role changes, and then click Invite.
To let people join your team without requiring an invitation, you can set up Approved Domains. With Approved Domains enabled, anyone can sign in to the team by using an approved email address—i.e., an email address from an email domain that a team owner has previously approved.