You simply need to install FileMaker 5.5 on the new machine. You'd need to find the installer software on the server and run it to install.
But this is an extremely old version of the software. The current version is version 13. Hope such an old version of the software will even run on your new workstation.
How does the client know where the server is? is there a preferences file that I need to modify to point it to the database
Nothing like that is needed. Pull down the file menu and select "Open Remote". You'll get a dialog listing all available FileMaker Servers on your network. Click one to select it and see a list of database files hosted on it. Select one and click "Open".
Note: this is how we currently do this and as far as I can remember, this was also how it was done with version 5.5.