Update README.md

Author: HadesD

README.md

@@ -2,6 +2,13 @@
 
 Direct complie c++ code in chrome
 
+# Install
+
+1. Download `release.zip` to your computer and extract it
+2. Open url `chrome://extensions/` in chrome
+3. Tick <kbd>Developer Mode</kbd>
+4. Click <kbd>Load unpacked extension… </kbd> and choose path of extracted extension.
+
 # Demos
 
 ![demo1](https://user-images.githubusercontent.com/11664992/28263122-9e3072c2-6b20-11e7-8aa5-f364c2a652c0.png)