Is this a monitor or an ANSI terminal? A monitor would connect using a DB/15 plug so it must be a terminal, with its own keyboard. Is that correct?
Try looking at the system startup messages using dmesg or by reading the /var/log/messages file. That should give you an idea about whether the operating system is detecting the terminal.
One possible problem with terminals is their baud rate. Make sure that your monitor is set up to use the same baud rate as the Linux tty devices. As I recall 9600 baud was a popular default value.
There must be a HOW-TO to setting up a terminal or external modem. Check http://www.tldp.org