Keep plugging away, they can be a pain.
DHCP should make things simple. When setting up a static IP you need to tell the router and maybe use whatever it allocated via DHCP as the static addy. You will need to look at the router and configure a static device there, and lastly on the voip.
Voip - log in using default credentials from any machine on your network, change login/passwd for security, select DHCP to make things easy, configure a line to hold whatever your voip provider says (very fiddly). Test, retry. On success consider a static IP and do this at the router first, suggest using whatever IP it allocates.
Your default gateway when you configure a static IP will be maybe 192.168.0.1 (ie the routers addy).
DHCP does everything automagically, done from your router, very easy.
Also check out the callcentric.com support, devices page for inspiration. It has an earlier device, should be similar.