First, create a method that can be used to print a bug. It can be done in any format you prefer, and use it to add and print a few bugs.
Implement a logging class. This class will take in an optional filename, but still log somewhere on disk if one is not provided. There should be a function that takes in a string to log to this file, and a function to close and open the logger.
Add logging to the application, so that every action is logged - from user creation, logging in, and the creation and disclosure of bugs. Also log when bugs are viewed from the system.
The logger class should also never delete old logs - only append to the log file.