You will be able to use your SLCs for your CBT as long as you don't already have a driving licence.
The idea is that it helps you become more mobile. If you are still at Sultan, pop into the Education Office and speak to the Education Assistant.
Edite to add: You will need to complete the form the Education Asst gives you, so your SLC for this year is registered.
Once you've completed your CBT, take the evidence of your pass (either your certificate or confirmation on headed paper from the training organisation) and complete the claim form. The money will usually appear the following month if you submit it before the JPA cut-off date.
This is actually at the discretion of your LO. He may well refuse you. On the ship I was on previous to this one the only people who were granted SLC's for driving etc were white mafia themselves, everyone else got knocked back, funny old thing that......