Add instructions to contribution

CONTRIBUTING.md

@@ -5,5 +5,10 @@
 * Make a new branch with your changes using `git branch -b <branch_name>`. For
  instance, if you are working on adding tests, you should do something like `git branch -b add_tests`.
 * Send in a pull-request.
+* Once you're done with the changes follow the commands to push to origin repo:
+  `git add <filename>`
+  `git commit -m "<Comment on changes made>"`
+  `git push origin <branch_name>`
+
 
 More instructions coming soon :)