The Addo API documentation describes Visma Addo web service and explains how to integrate with it.
The integration to Visma Addo is via Rest API. SOAP can be offered.
If desired, a developer resource can be contacted if you have questions or need help with the API integration. This is usually free of charge, but Visma reserves the right, by prior agreement, to invoice part of the time spent on larger projects.
After the development has been completed on the demo environment, a similar environment can be created with integration user on production.
API documentation and other information can be found here: https://github.com/vismaaddo