Open DNS Manager, right-click the DNS server you want to add a forwarder and click Properties.
Select the Forwarders tab and click Edit.
Specify the IP for the forwarder and click OK.
The forwarder has been added. Click OK.
You can do the same with PowerShell.
Add-DnsServerForwarder -IPAddress 192.168.122.42 -PassThru
To get the forwarder setting with PowerShell use get-dnsserverforwader