Hey Juvvy!
Have you already got a NIC for it?
You'll need something like an RTL8029 10Mb Ethernet card (I don't think your Prometheous supports 100mb cards?)
I guess you have a driver CD with the Prometheous?
Install as per the instructions (assuming it has some :readit
I suggest use MiamiDX, its included with Classic Workbench and you'll find it in the 'my files' drawer.
Its the easiest TCP/IP stack I found to setup as it has an auto install/setup procedure. So after you installed the program run 'Miamiinit'
Hopefully step by step it will auto detection of your settings, if not you can enter them manually as you go, I had to do this for my Mediator PCI's whereas the Netgear PCMCIA card picked them all up on its own...
So it would be useful to have:
IP address of the Amiga (mine was 192.168.1.101)
Subnet Mask (Mine was 255.255.255.0)
Gateway (Mine was 192.168.1.254)
DNS Server/s for your ISP (Mine was 87.194.0.51)
Once you have saved your configuation you can run MiamiDX and import your setting and then save them as default, you should at this point be good to go and hit 'online'
I know I don't have the experience of setting up a Prometheous, but I hope this info helps in some way.
Steve.