This is applicable to my VPN; it might not be applicable to yours. Hope it at least helps.
In System Preferences, go to the Network pane.
Click the dropdown menu next to "Show" and select "Network Port Configurations." Check the checkbox next to "VPN (PPTP)."
Click next to "Show" again and select "VPN (PPTP)."
On the TCP/IP tab, set "Configure IPv4" to "Using PPP." You can fill in the provided DNS server information (probably one or more IP addresses) next to "DNS Servers" in this window. If you were provided domain names or IPs for search domains, fill those in as well. Otherwise you're done with this part.
Run the application "Internet Connect." It's located in Applications, or you can get to it from the Airport or Bluetooth menu bar icons.
Click the "VPN (PPTP)" icon at the top.
Put in the server address (the actual IP you connect to), and put in your login information (this is the same user name and password you'd use to log in to the network on a local Windows machine). Check "Show VPN status in menu bar."
Click "Connect" and see what happens. You should see "Contacting VPN server" then "Authenticating" then "Connected to" and "Connect time" at the bottom next to "Status," and the "Connect" button should change to "Disconnect."
Important: Go to the "Connect" menu and select "Options." Make sure "Send all traffic over VPN connection" is NOT checked; otherwise your regular internet connection will slow way down as it all goes over the VPN to the remote network!
You're now connected to the network just as if you were in the office.
You should also have been provided an IP address for the network drive you need to access. To connect to it, go to Finder and either do command-K or select the "Go" menu then "Connect to Server."
Type "smb://" followed by the IP address of the network drive at work. If you type just the IP address, it will default to "afp://" which is the Apple networking protocol; you need to specify "smb://" so it connects using the protocol the Windows server will understand.
The remote network drive should then appear as a drive icon on your desktop, and you should be able to access it just as if you were in the office.
Like I said, this is how mine is set up. Hopefully it will give you a starting point and if it doesn't work there is someone at your office who can help.
You shouldn't have to worry about the WINS information specified, by the way. That stands for Windows Internet Name Service, and should only be necessary with Windows clients and Windows servers running software *older* than Windows 2000 and Windows 2000 Server.
Check Wikipedia entries for WINS, Apple Filing Protocol, and Server Message Block (as well as the other terms) for more details on what those are. My knowledge is based 100% on the struggle to get my own VPN connection up and running!
