To start receiving email for your domain, you will need to change the name server to us. If you prefer to manage your own DNS, you can simply set/update the MX record for your domain.

First, login to RYO and navigate to the upgrades section. Next to your domain, you will see further instructions and you will see what nameservers to use next to your domain.

What's the difference between changing the Name Servers or MX records? Changing the Name Servers is the easiest option, and we'll manage the DNS zone for you. However, we only have limited DNS management options. If you want to manage the DNS zone yourself, you can edit your DNS zone to add an MX record.

What's an MX Record - http://en.wikipedia.org/wiki/MX_record

Name Server - http://en.wikipedia.org/wiki/Name_server

To change the Name Servers, see:

Or to just change the MX record

To change Name Servers

https://support.godaddy.com/help/article/664/setting-nameservers-for-your-domain-names