add 'how to use' to README file

Author: omidnikrah

README.md

@@ -1,2 +1,7 @@
 # anonymous-instagram-story-seen
 Seen Instagram stories anonymously
+
+# How to use 🤓
+1. Download the project by [this link](https://github.com/omidnikrah/anonymous-instagram-story-seen/archive/master.zip) and extract it.
+2. Go to chrome://extensions/ and turn on developer mode
+3. Click the Load unpacked extension button and select the unzipped folder for your extension to install it.