Using the BH1750 with Arduino is a simple matter of wiring up the sensor to your Arduino-compatible microcontroller, installing the hp_BH1750 library written by Stefan Armborst, and running one of many very well written examples. Usually we write our own library but we were so impressed by Stefan's that we didn't think we could possibly improve on it, so use it!
Use this wiring if you want to connect via I2C interface. The I2C address address for the BH1750 is 0x23 and can be switched to 0x5C by pulling the address pin high to VCC
Here is how to wire up the sensor using one of the STEMMA QT connectors. The examples show a Metro but wiring will work the same for an Arduino or other compatible board.
Here is how to wire the sensor to a board using a solderless breadboard:
You can install the hp_BH1750 library for Arduino using the Library Manager in the Arduino IDE.
Click the Manage Libraries ... menu item, search for hp BH1750, and select the hp_BH1750 library:
To show the fundamental feature of the sensor, measuring the ambient light in lux, you can use the modestly titled "BareMinimum" example:
Open File -> Examples -> hp_BH1750 -> BareMinimum
After opening the demo file, upload to your Arduino wired up to the sensor. Once you upload the code, you will see the Lux values being printed when you open the Serial Monitor (Tools->Serial Monitor) at 9600 baud, similar these measurements I got from waving a flashlight at the sensor