Update README

README.md

@@ -37,6 +37,18 @@ pip install --upgrade pip
 pip install -r requirements.txt
 ```
 
+## Building the Notebooks 
+
+The notebooks are generated by the tool in `tools/gen_questions.py`. The notebooks are generated from Python source that contains markdown for a question and the correct answer. The answer is used to generate a preview inside the notebook that shows what the correct answer should look like. The preview is an important prompt to help students know they have the right answer. 
+
+The notebooks are not checked into Git. They are generated using the `makefile` in the root of this project:
+
+```sh
+make 
+``` 
+
+## Viewing the Notebooks 
+
 Run Jupyter:
 
 ```sh