In order to try out Metropolis you'll need to use a telnet client. A telnet client will allow you to access Metro as if you had dialed it up with your modem, but you will be actually accessing it over the internet. A window will open up (called a terminal window) and you will be able to interact with the BBS through that window while logged onto the BBS.
If you don't have a telnet client yet, we would like to recommend EWAN for PC users and MacBlue for Macintosh users. For your convenience you can download either of them here on the Metro website