What I understand is that the DeviceConnectionProvider provides you a DeviceConnection object with the method getConnection(ConfigurableDevice device).
After, you can connect to the device with this object: deviceConnection.connect(DeviceConenctionCallback).
Once connected, you can access the settings with: deviceConenction.settings.beacon.transmitPower.get(SettingCallback).
If you want to change the settings, use: deviceConnection.settings.beacon.transmitPower.set(Integer, SettingCallback).
Note the possible values for the setting.
A complete code (after recovering the ConfigurableDevice):