Update Contributing.md with quickref update instructions (microsoft#763)

.github/CONTRIBUTING.md

@@ -13,6 +13,7 @@ We're so glad you asked!
    * [Contributing new katas](#contributing-new-katas)
    * [Style guide](#style-guide)
    * [Updating the Katas to the new QDK version](#updating-the-katas-to-the-new-qdk-version)
+   * [Updating the Quick Reference](#updating-the-quick-reference)
    * [Validating your changes](#validating-your-changes)
       * [Excluding individual tasks from validation](#excluding-individual-tasks-from-validation)
       * [Validating changes to `%kata` and `%check_kata` magics on local machine](#validating-changes-to-kata-and-check_kata-magics-on-local-machine)
@@ -115,6 +116,15 @@ Updating the Katas to a different QDK version can be done using PowerShell scrip
 
 After running this script you should validate that the update didn't introduce any breaking changes; see the next section for how to do this.
 
+### Updating the Quick Reference
+
+You can update the Quick Reference by making your changes in the [`.tex` file](../quickref/qsharp-quick-reference.tex). 
+After you do your changes, compile the `.tex` file into a `.pdf` file and include both files in the pull request. 
+(The changes to the `.pdf` file will not be shown in the pull request, so be careful not to introduce any changes not included in the `.tex` source!). 
+To complile your `.tex` file into a `.pdf` you will need a compiler, such as [MiKTeX](https://miktex.org/download). 
+MiKTeX includes a simple IDE that gives you a user interface to compile the `.tex` file. 
+MiKTeX will also pull in all the required packages to compile the `.pdf` file.
+
 ### Validating your changes
 
 When you contribute any code to the Katas, you need to validate that everything works the way it is supposed to work. Here are the key points to check (they might or might not be applicable to your change, depending on what you modified):