Rotuing ADSL thru network switch. Help!

Hi guys.
I need your help configuring ADSL throughout switch.

This is the story:
My company obtained ADSL throughout ISP. Modem, which is router at the same time, is some Sagem model.
Modem is connected on switch that stands in communication case which has 3 more, 24 port Allied telesys, switches.

All of the PC's that are in the network have static IP addresses because we do not have DHCP server. Server that we have is UNIX based for terminal app/database. And it is used only for that.

Now, we want 5 computers to go onto internet thru ADSL.

ADSL IP address which is 192.168.1.1

I added onto 5 computers additional IP addresses with subnet mask (255.255.255.0) that correspond ADSL. (examp: PC1 192.168.1.3, PC2 192.168.1.4...etc.)
These 5 PCs now have ability to connect to modem fro setup via 192.168.1.1 IP. And this is the only way that works.
But still we cannot go to internet.

I checked WAN address which is something like 213.xxx.xxx.xxx, I'm not at work so I cannot tell what WAN address is.

In Modem setup, I found Route option, but when I try to add IP addresses that are in 192.168.1.3 to 7 with subnet mask and either pppoe or LAN0 option, when saved/applied it gives me some error 1, and that it cannot be added.

Can you help me on this?

Thnx in advance.

Change one of the PCs to DHCP, get an IP address from the modem/router, run ipconfig/all to find all the network settings and then reset the static IP using those settings.