After you have added your Managed domain to NSONE, you will have to complete the following steps in DNS Made Easy.
1. Create an IP set - Once configuration within the NS1 portal is complete, you must configure the secondary servers to use xfr01.nsone.net (188.8.131.52) as the primary server for the zone.
3. Once the secondary domain is added, click on the domain and grab the IPs under the IPv4 table.
4. You will want to add the IPs retrieved in DNS Made Easy to the zone in NSONE. You can accomplish this by clicking on the 'Zone Transfer' option and pasting our IPs within this interface.