Hello Ian,
Congratulations on completing basic indoctrination.
Now that you’ve completed BI, the 737 systems testing is available to you.
It’s broken down into 15 separate quizzes based on each system chapter from the Boeing 737 Operating Manual Volume II.
Once you work your way through all of these you’ll be well-versed in all of the aircraft systems, as this is all based off of real-world testing material for pilot training.
Let us know if you run into any difficulties or if we can be of any assistance!
Mike