Joining Instance to AWS Directory Service Directory

Hi, I'm following an AWS walkthrough to join an instance to to AWS Directory Service Directory (http://docs.aws.amazon.com/fsx/latest/WindowsGuide/walkthrough01-prereqs.html)......part 3 talks about changing the preferred and alternate DNS server addresses to the AWS Directory Service ones)
I have created my directory, but I don't know where to find the DNS server addresses provided by the AWS Directory Service
Can anybody help with this?
Any assistance gratefully received