To create a new user which syncs across all VMs in the tenancy, you need to create it inside the LDAP.
There are two ways to do it:
Run the Create a new LDAP user inside Morpheus
Head over to the Provisioning tab in Morpheus and click your LDAP instance.
Select Actions > Run Workflow > Create a new LDAP user.
Fill in the values, and do note that the public SSH key is mandatory. Below is a screenshot of a correctly filled workflow.
The user will be prompted to change their password upon first login after successful creation and the minimum lifetime of password is set to 1 hour.
Create a new user by accessing the LDAP itself
To create a user manually (this might be needed if you need to customize access to VMs, reset passwords, etc.) you can follow the guide at: EUMETSAT tenancy: Default setup or the last steps in Deploy FreeIPA LDAP and internal DNS service.