This depends on which service you are signed-up for, and your accounting system. For Dynamics GP users, you get a Fidesic for Dynamics module that you install. This adds a few windows inside Dynamics GP, and you are good to go. Typically, this install takes less than 5 minutes, and does not require IT personnel.
If you are using other QuickBooks, Enliven provides you with the Fidesic Sync Module which integrates with both QuickBooks Online as well as QuickBooks Enterprise.