[TASK] update installation commands

docs/INSTALL-NODE.md

@@ -15,7 +15,11 @@ To activate nvm, you need to source it from your shell:
 
     source ~/.nvm/nvm.sh
 
-You should add this line to your .bashrc file. Remember to reopen your terminal after you modified .bashrc.
+You must add this line to your .bashrc file. Remember to reopen your terminal after you modified .bashrc.
+
+```bash
+    echo "source ~/.nvm/nvm.sh" >> ~/.bashrc
+```
 
 To install a specific version of Node, you can run 'nvm install [node-version]'. This project requires Node v0.12.x. To install this version, run: