Adding your people and inviting them are covered in one article: Adding your people and sending invitations.
In short:
- Go to People → All people and choose Add people, then A file or Add a person. Adding someone sends nothing until you choose to invite them.
- Choose Invite on a person's row, or tick several people and choose Send invitations (the button shows how many, such as Send 12 invitations). The link in the email works for 7 days, and Invite again sends a fresh one.
- Each person shows as Added, Invited, Active or Deactivated, and the Extension column shows whether they've installed the browser extension.
For what each role can see and change, see What each role can do.
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