Update README.md

Author: Surajit A Bose

README.md

@@ -3,6 +3,8 @@ Instructions for Practice Project
 
 These instructions assume familiarity with Git and GitHub. If you are not comfortable with those tools, please complete Udacity's [How to Use Git and GitHub](https://www.udacity.com/course/how-to-use-git-and-github--ud775) course before proceeding. 
 
+After installing the required tools, you will need to ensure that your computer can find the executables to run them. For this, you might need to modify the PATH environment variable. A good overview is at [superuser.com](https://superuser.com/questions/284342/what-are-path-and-other-environment-variables-and-how-can-i-set-or-use-them). You may need to search the web for instructions on how to set the PATH variable for your specific operating system and version. 
+
 ## Setting up your local machine
 
 * Install [VirtualBox](https://www.virtualbox.org/wiki/Downloads)