Registration starts in September, but you can start looking at most of the materials now. As Jacek says, you will not be able to access the scores for levels D04 and above until you have enough posts to join the 020 group, but the good news is that you can already access the scores for the first three levels, and can view the existing lesson topics here
for all levels. Have a look at the four posts starting here
for some advice and useful links given to another member in a similar position. If you have any further questions about registering, that is the best place to ask, and the lesson moderators will be able to advise you further.
Classical Guitar Forum.
"Experience is something you don't get until just after you need it." - Steven Wright