There's a
form on the website.
Once you get your login details, you should phone up and book accred 1+2 on the same evening (you can't do that on the website). I checked the system just now, and there is zero waiting time for the Tuesday evening sessions.
I spent a couple of hours at the bike show in the morning. Got myself signed up for the Pedal for Scotland sportive with a discount, and picked up a massive freebie pack from High5 - I sometimes struggle to understand how those guys run a profit, considering the amount of free stuff they seem to hand out.