Only Administrators can invite new users to a team.
Steps to invite new user:
Click account drop down menu and choose “[Team name] settings”
Click the green button in the top right corner "Invite new user".
In the form you see please enter your colleague's email address and name (not necessary).
Also, choose the groups you want her to take part in. You can choose some of the default groups (Accounting, HR, Sales, Marketing, IT) or create a new group. Type the group name and click "create group [groupname]” link on the drop-down panel. You can choose multiple groups.
When you click "send invitation", your colleague gets an invitation email with the link to login.
Until she signs up to Metatask, you can both resend invite or cancel it. But you cannot yet assign tasks to her.
Once your team member signs up, she is available for tasks and you can start working on your first project together 🙂