diff --git a/README.md b/README.md
index 07677c6..5052960 100644
--- a/README.md
+++ b/README.md
@@ -99,3 +99,12 @@ https://github.com/Atlas-Scientific/Ezo_I2c_lib
 Again, it is important you **do not unzip** the downloaded file. One more time, you have to import this file 
 to the Arduino IDE by following the same instructions: **Sketch > Include Library > Add .ZIP Library**
 
+## Source code 
+After you import both .ZIP files, in this repository it is included the file **source_code.ino**. You must 
+download this file and open it in the Arduino IDE.
+
+Once you have the file opened, the first thing to do is filling in the code with the name of your Wi-Fi signal and 
+its password. Also, it is neccessary you complete with the data from the ThingSpeak platform, specifically for 
+the **Channel ID** and your **Write API Key**.
+
+![Filling in wifi password](14.png)