The API consists of two classes "sdnsNetAPI" and "zone". The sdnsNetAPI class contains all needed functions to interact with Simple DNS Plus. The zone class is just a definition for a dns zone. To create a new zone called "mynewdomain.com" on your primary and your secondary (if available) nameservers, just use the zone constructor and provide the zone information, i.e:

Dim sdpApi As New sdnsNetAPI("ns.yournameserver.com", "yourPassword")
Dim myZone As New zone

myZone.PrimaryNS = "ns.yournameserver.com"
myZone.SecondaryNS = "ns2.yournameserver.com"
myZone.DomainName = "mynewdomain.com"
myZone.WebserverIP = "123.123.123.123"

sdpApi.updatePrimaryZone(myZone)