Navigate to Settings by clicking the hamburger menu in the top left and selecting "Settings".
Under "Organization", select "Users".
Click the "Add team members" button. This will open the "Invite people" dialog.
Enter as many emails as desired, either one per line or separated with commas.
For each listed role, check the box if the people you're inviting should have that role and its associated permissions.
Click the "Send invitation" button.
Invitation emails will be sent to the listed email addresses. These emails contain a "SIGN UP" button the users can click to set up their account and join your organization.
People whose invitations have not yet been accepted will display with "Invited" in the "Last active" column.
If necessary, you can delete a pending invitation by clicking the menu button in that row and selecting "Delete invitation".
Click the row of the user you wish to manage. This will open the "Edit roles" dialog.
Check or uncheck the role boxes as appropriate to grant the desired roles and associated permissions.
Click "Apply".
Click the menu button in the row of the user you wish to manage.
Select "Remove".
Click "Remove from the team" to confirm.