The Console application is a tool provided in OS-X's Utility folder. It allows access to to virtually all of the UNIX log file and things like OS-X crash reports. The image below shows the console application open to the system.log file:
Using the Console application to obtain the crash report file: In the Console application there is a drawer on the left side as shown below:
In that drawer you will see a list of crash reports in this example associated with WeatherCat.
If you use your contextual menu (typically "right-click" on your mouse) it will bring up the following menu:
What will then pop up is a regular Finder window with the particular crash report selected. You can now copy the file by drawing it to the desktop (while holding the option key.)