Update readme

README.md

@@ -4,6 +4,44 @@
 
 This is the Dockerfile (etc.) used for building the image that runs python scripts on Kaggle. [Here's](https://registry.hub.docker.com/u/kaggle/python/) the Docker image on Dockerhub.
 
+## Getting started
+
 To get started with this image, read our (guide)[http://blog.kaggle.com/2016/02/05/how-to-get-started-with-data-science-in-containers/] to using it yourself, or browse [Kaggle Kernels](https://www.kaggle.com/kernels) for ideas.
 
+## Requesting new features
+
 **We welcome pull requests** if there are any packages you'd like to add!
+
+We can merge your request quickly if you check that it builds correctly. Here's how to do that.
+
+Start by running this image on your system:
+
+```
+me@my-computer:/home$ docker run --rm -it kaggle/python
+root@d72b81a003e1:/# 
+```
+
+Then follow the package's installation instructions for a Linux system. It could be as simple as installing via Pip:
+
+```
+root@d72b81a003e1:/# pip install coolpackage
+Collecking coolpackage
+[...etc...]
+```
+
+Once that's done, check that you can import it correctly. (Sometimes, if a package is missing a dependency, it throws an error when you try to import it.)
+
+```
+root@d72b81a003e1:/# python
+Python 3.5.2 |Anaconda 4.2.0 (64-bit)| (default, Jul  2 2016, 17:53:06)
+[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import coolpackage
+>>>
+```
+
+Once that's working, add the necessary lines to our `Dockerfile`. (In this case, that would mean adding `pip install coolpackage` to the end section of the Dockerfile.) Then submit your pull request, and you're all set!
+
+
+
+