Adding first first to contribution.md.

CONTRIBUTING.md

@@ -35,5 +35,15 @@ git branch -r
   origin/master
 ```
 ### Making the first push
-When you are ready to push your changes
+When you are ready to push your changes, you will get a fatal error about `no upstream branch`.
+```
+git push
+fatal: The current branch contribution_guide has no upstream branch.
+To push the current branch and set the remote as upstream, use
 
+    git push --set-upstream origin contribution_guide
+```
+Follow the suggested command
+```
+git push --set-upstream origin contribution_guide
+```