During signup you will have the option to select a full contact sync, or to start with an empty address book in Covve.
If you start Covve with the syncing enabled, then Covve will sync 2-way with all contacts on your device. In this scenario, Covve will sync with all available contacts. At the moment there is no way to choose a specific contacts account, or a subset of contacts.
You have the option to start empty without syncing with your phone's contacts. So you can start with an empty address book, and add your contacts either by scanning business cards or adding them manually.