How to connect to AWS EC2

I'm trying to connect to AWS EC2 GPU server to run my Matlab source code. and I followed the steps on matlab-on-ec2.pdf downloaded from Matlab website.

when connecting EC2, then get a popup with a box to enter 'passphrase for key 'users/.../.nx/temp/.../keylog', but I don't have a passphrase associated with my private key on EC2, if I open the file 'users/.../.nx/temp/.../keylog', contents are same private key file that i downloaded from aws website.

I tried leaving it empty or instance ID, neither of them works,

[Gareth Stevenson]

In order to try and help you I was wondering if you could tell me which page of the PDF you are getting stuck on? Are you using an NX Client to gain access to the instance?