Pointers for configuring vpn please

[<colin helliwell ln-systems com>]

I'd like to get NM VPN connections going on my platform. 
We have a VPN for dial-in from home, so I'll just test out with that to
begin with. We use a Draytek vpn client on Windows, which is configured for
PPTP with the necessary username and password.
I've built/installed the NetworkManager-pptp plugin, but could I get some
tips please on how to manually (editing/nmcli - no gui) configure a vpn
connection?  (The errors from what I've tried so far aren't too informative
- reason="Could not find source connection.")
Not too concerned about the securest/cleanest way to configure the
connection settings - just want to verify that I've got all the necessary
components installed.