Revise upload instructions for Nano Matter

Updated instructions for uploading code to the Nano Matter.

Author: rei-vilo

content/hardware/03.nano/boards/nano-matter/tutorials/01.user-manual/content.md

@@ -145,7 +145,7 @@ void loop() {
 
 In the Nano Matter, the `LED_BUILTIN` macro represents the **red LED** of the built-in RGB LED of the board. Please refer to the image below.
 
-To upload the code to the Nano Matter, click the **Verify** button to compile the sketch and check for errors; then click the **Upload** button to program the board with the sketch.
+To upload the code to the Nano Matter, first call the menu **Tools > Programmer** and select **OpenOCD**; then click the **Verify** button to compile the sketch and check for errors; finally click the **Upload** button to program the board with the sketch.
 
 ![Uploading a sketch to the Nano Matter in the Arduino IDE](assets/compile-blink.png)
 
@@ -2035,4 +2035,4 @@ Join our community forum to connect with other Nano Matter users, share your exp
 
 Please get in touch with our support team if you need personalized assistance or have questions not covered by the help and support resources described before. We're happy to help you with any issues or inquiries about the Nano Matter.
 
-- [Contact us page](https://www.arduino.cc/en/contact-us/) 
+- [Contact us page](https://www.arduino.cc/en/contact-us/)