You need your private keys @stapies, this is a fundamental basic to all ICO's and even when they say you don't need to send from your own wallet where you have private keys, I still recommend it.

You might be able to contact the exchange and ask them to provide you the private keys. They might or they might not, but you have to hope they do I guess.

Hopefully the NVO team replied by now. Go to https://nvo.io/#contact and see some other options to contact them if still need assistance.