I suggest you not to use the DDNS provided by viewnetcam.com, use dyndns.org instead. After you register an account and domain name in dyndns.org, put your account, password and domain name in the DDNS page of your router.
As for UPnP, enable it on both the router and the IP cam. However, this may not mean automatic port forward setup of your IP-cam at your router. You may still need to manual config the port forward setting at your router. As for the ports need to be forwarded, check the IP cam manual for details.