To add a user to your Fastned account, go to the Fastned app and in the profile section, select: My settings > Users > Add user.
The newly added user will receive a text message with a temporary password. He/she can then login with the phone number and this temporary password, and will then be able to set up his/her account.
Note: if you see this error message:
Whoops, this phone number has already been registered or has expired due to inactivity. Do you want to log in with this number instead? → This user most likely already has their own Fastned account. You can ask them to login or contact support to close the account.