Finish preparation.md

[JosephMcArthur]

[//]: # "=======================
Instructions for posting issues:
(1) Review what is already there. Perhaps a comment to an existing issue would be more appropriate than opening a new one? Issues can be a topic idea, a cry for help, an introduction to yourself, a to-do, or a discussion / question about the event itself.
(2) Write your post below the "==" line at the bottom of this text blob using Markdown (as per https://guides.github.com/features/mastering-markdown/ ) or just plain text.
(3) Don't worry about these introductory lines - you can leave or delete them, as they won't display anyway (you can check this via Preview).
(4) Hit the 'Submit new issue' button.
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