You must register as a ninja and then you must book your ticket in advance to attend a Coder Dojo session:

Go to the CoderDojo website to book your tickets in EventBrite:  CarrickOnShannon CoderDojo

Notice that you need to register first on the coderdojo website also. If your child is under 12, parents need to register and then they need to add their children as a youth. 

Online help is available here: Community Platform Tutorial: Registering an account & editing a profile (Parents,Youth,Champions)