Update README.md

README.md

@@ -16,6 +16,20 @@ Out[2]: 32
 
 and so on and so forth.
 
+Two notes:
+
+1. In order to use the library like this, you need to be in the root directory (that is, the directory that contains the `scratch` folder). If you are in this directory, the imports won't work.
+
+2. It's possible that it will just work. It's also possible that you may need to add the root directory to your `PYTHONPATH`, if you are on Linux or OSX this is as simple as 
+
+```
+export PYTHONPATH=/path/to/where/you/cloned/this/repo
+```
+
+(substituting in the real path, of course).
+
+If you are on Windows, it's [potentially more complicated](https://stackoverflow.com/questions/3701646/how-to-add-to-the-pythonpath-in-windows-so-it-finds-my-modules-packages).
+
 ## Table of Contents
 
 1. Introduction