How can I make a graphical password authentication minor project?

Start by deciding which language you are planning on using! :laugh:
Then, start by preparing a specification - describe exactly what you expect the app to do, what it should look like, how the user can interact with it.
Then "flesh that out" by working out how data flows round the app, what data you need to refer to, and start working out what operations that mean you need to implement.
That should give you the overview of the modules and classes you will need, ready for you to start writing them.
It's the same as any other project you've done: just possibly a bit bigger and more complex looking.