(aside; you don't mention what the server you want to connect to is running! OS X Server? Windows Server? Any-Old-Windows pretending to be a Server? Linux? FreeBSD? Solaris? Irix? Unix? Minix? VMS?!?!)
generally...
You might look into VNC, which gives something similar to windows remote desktop.
If you really are talking about a server, and want its network drives etc only, then VPN is the way to go.
Either way; whoever admins the server should be able to help you / set it up for you / tell you you're not allowed to do it.
If you are the person who handles the server, and you don't recognise VNC / VPN and have some idea of what they do, then you're not going to get it set up in time
In short, both let you connect to your office network remotely:
VNC by running a service on the office server that handles the incoming connection and lets you log onto the machine as if sat at it, this service needs to be NAT forwarded to the server by the router.
VPN runs as its own virtual server (probably still as a service on the server in question), and it allows you to log your remote machine onto the office network as thourgh you were in the office. This would also need the appropriate NAT forwarding on your router.
Again; whoever is in charge of the router should know how to setup NAT for a service. If its you, and you don't; read your router manual!
I run VNC on my home network (internally, not using NAT) to connect to my mac mini. I run
osxVNC on the mini as a server and
Chicken of the VNC as the client on my powerbook. (I have no clue how they got that name!) I've not wanted to make external connections.
I've looked into VPN before now, on windows, and it wasn't simple to configure the first time. (in fact I gave it up as more work than it was worth).
I have no clue how to configure VPN with macs.
