If you have never been on a public road before, we would strongly advise practicing the motorcycle theory test or the Ride Free pre CBT course to gain extra help with the Highway Code/road safety information.
VERY IMPORTANT! Just because you have safely completed a Compulsory BASIC Training course, this does not mean that you are automatically ready for a full bike licence!
Unless you already have lots of previous experience then it is quite usual for a training school to recommend top up lessons or buying your own 125 to gain further experience, before the "pressure" of a full licence course.
If you have not taken a full licence in the following two years, then you have to repeat the C.B.T. course to continue riding as a learner. At age16 you can only ride a 50cc moped, at 17+ you can ride a 125cc.
Talk to your local training school about any of the above steps. If you have any concerns they will be able to answer them for you. If you're wanting to ride a bike larger than 125cc, then this would involve first passing the motorcycle theory test (just the same as you would before taking a full car licence)
Your training school will best advise you of the amount of training that you require as an individual before taking the full motorcycle licence. This is usually done at the end of a satisfactory CBT road ride.