Update readme

Author: duongvituan

README.md

@@ -4,6 +4,17 @@ Simple app code by [Godot Engine](https://godotengine.org) to create grid image.
 
 ![GridImage](https://github.com/duongvituan/GridImage/blob/main/image/sample.png)
 
+You can use it to create grid images, making it easier for you to draw.
+
+![GridImage](https://github.com/duongvituan/GridImage/blob/main/image/draw_sample.png)
+
+
+## How to open end edit source code
+
+1. Download [Godot Engine](https://godotengine.org) version 3.x
+2. Download source code Grid Image.
+3. Use Godot to open file project.godot in source code Grid Image.
+
 
 ## Contribution