Invitations for users to sign up can be managed using the invitation management console.
From the Tools menu (cogwheel icon), go to Manage invitations.
The invitation management console contains all open invitations to individual users, organizations, or public links that anyone can use. Note that individual user signups will disappear from the list once the link has been used once (the link expires). Organization invitations and public signup links (correspondingly labeled in the management console) remain active until revoked.
Getting the signup link
To get an active signup link, click on the signup link in the console. For example, the link will be copied to the clipboard and can be pasted into an email.
Revoking a signup invitation
Select the Revoke link next to an invitation to revoke the signup link immediately. Users attempting to use it will be notified that the link may no longer be used.
Seeing who has signed up
When users have signed up using an organization invite or a public link, a Redeemed by... button is displayed next to the invitation. You can select this to see which users have been registered by following that invitation link.