1. If not already done, download and install the Arduino software (IDE) for the required OS. (Windows, Linux or Mac instructions)

2. Configure the IDE to the desired board.

See Getting-Started#configuring-ide

3. Open the Blink sketch from the "File> Examples > 01.Basics > Blink"

4. Click the upload button

See Getting-Started#upload-method to change the upload method.

That's all. LED should blink on the Nucleo L476RG.