You must be logged in with your own credentials.
Press "Hi, your name"
And from there user Management.
Here you enter the subuser's email and choose either full rights or limited rights for new subuser. You are free to decide what he has rights to.
And when you have selected the rights, send the invitation.
Now the new subuser has to accept the invitation by clicking the link.
A new sub-user must register him/herself on Tietokettu's website or have already registered with him/her own e-mail
If you register, be sure to check the box: I have read and agree to the Terms of Use