In order to send and receive data between Sitefinity and MS Dynamics, you need to select what entites you wish to use with Synx. This can be done via the Entities screen of the provider. See Accessing the entities screen
The entities screen displays a list of all available entities in MS Dynamics that can be synced with Sitefinity. Once synced they will be available for use in Synx page and form widgets. See Selecting entities to use.