The Bluetooth connection allows you to configure your timepiece from a smartphone. It is also used to in complications such as diary reminders and share prices.
To connect to the phone, press the top pusher and press Connect in the phone App. It will connect and then you can configure features such as Time Zone. Current time, & date, daylight saving, etc are automatically set when you connect. When you're done, press Disconnect to disconnect to prolong battery life.
The watch will reconnect automatically at regular intervals to keep updated, so leave the App running on your phone so it can reconnect. The frequency of reconnection depends on the type of complications on the watch. You can modify the reconnection frequency in the Advanced Settings section of the App.
The range is approximately 10 meters (33 feet). If you go out of range and the connection drops, it will reconnect when scheduled,. If you want to reconnect sooner, you can do so manually from the phone App.