Well you can either telnet to the linux system, or preferably SSH to the system because with telnet you can easily be sniffed (not good... root password easily gained this way).

In order to Telnet or SSH into the system, use Secure CRT (SSH), CRT (Telnet), Putty (free and can SSH) or any one of several available programs.

If you would prefer to look at the system in a more GUI surrounding, use X-Win32 or Exceed or any similar program.

If you want you can also tip into the system using a null modem cable... but that can be a pain and you need to have physical access to the system.