Talking to a server

Well I am very new at this so forgive me if my question seems very simple to you it isn’t to me.

I have a Sun Ultra 5 running Solaris 8 and I bought a Sun Ultra Enterprise 2 machine it does not have a video card. So I got a null modem cable to connect the 2 machines now comes the problem I do not have any idea on how to make them talk. The Enterprise 2 does not have an operating system on it, I would really like to load one on.

Please Help