To register companies automatically, you can import them from Isah. This will only work if they have been configured for Supply Chain Integrator: they must be registered in the Companies form, a customer and/or supplier must be specified on the Supply Chain Integrator tab and they must have at least one unique identification (SCSN code, GLN, COC or VAT).
Only companies that have not been added to the My companies form yet will be imported. Companies that have already been registered will be updated with data from the Companies form, if necessary.
If you want your own companies to be able to send each other SCSN messages without needing authentication, check the Settings tab to see if authentication is set correctly. If you want your own companies to use authentication, toggle the setting to 'My companies need authentication to process messages'.