In Accounting systems you can choose from the drop down list.
Please note that we keep growing the list with time.
Accounting system is used to connect to some of them but the others are set up through Developers Key.
Check out our Integrations page for a list of accounting system connections and how to set them up: Integrations
Note: If we do not have direct connection to the accounting system your property is using, check out Omniboost as they can connect to multiple accounting systems that can then be connected to SyncNbook.