The feature to add/change additional users has not been released yet, however, it is coming very soon - around June 2018. When this feature is live, you will be able to add several users to your bank account and set custom roles & permissions for them. The users will also be able to order their own Penta card linked to your company account.
Please check out our product roadmap to see the most up-to-date information on when this feature is coming. You can also vote for it right on the roadmap and we will try to make it happen sooner.