Orchestra has some drawbacks when it comes to handling a lot of users, branches or services. The import feature mitigates that somewhat. The idea is that you download the template for the area you want to import. There is a link on the page to a template csv file:
When you have filled it with the users, branches or services, you attach it and press Preview. That will let you validate that you have done the file right. Then you need to press Import to actually import all of them.