Hi Sar
Congrats on passing recruitment. As the other guys have mentioned you will learn operational rules, starting initially with PTS (Personal Track Safety). After PTS which you MUST pass you will then go on to learn rules, depending on the company can range from 14 weeks up to 6 months. Then you will go on to traction and learn all about the train itself, after that you may be required to do a short course on principles of route learning which is to help you use techniques to help you learn a route/s. Then you will be placed with a driver instructor and then fulfil a required amount of hours including dark time as per company standard before passing out as qualified. There is alot to take in and hard work to put in but worth the reward in the long run.
Don't try and read up on rules materials in advance as trainers will take you through a structured learning. However you must be able to pass PTS first, concentrate on PTS then follow trainers. If you want to read up on PTS for driving grade then check out the following link as its free and accurate.
https://uktrainingsolutions.com
Good luck with your career..