I just started reading about FI-WARE, so this might be a very noob question.
A beacon is basically a device that just uses bluetooth for pushing info about its position.
How should it be connected to a generic Enabler, for instance a a POI Data Provider, an Iot Broker or a POI GE?
Shall it first send its coordinates to a mobile device via bluetooth and then this device is supposed to send this value to the Iot Broker? If so, how?
A bluetooth beacon is much simpler than that. It is merely a device that transmits a unique identifier constantly. Because the identifier is unique, you can tie it to a specific location using external databases or information sources embedded in a mobile app.
Integrating with external systems like you describe is a process completely outside the beacon's responsibility. You must go through a process to manually associate the beacon's unique identifier with such systems when it is deployed.