Best Idea would be to get a router... one connection into the router and you can plug in up to 4 hubs as big as you want....
Anyway, right now you have 4 ports on your hub, your uplinks taken because of the DSL modem and you cant connect the 4th port because its a rule of hubs.. just going over everything, now the other 3 ports are used.. if you want to add another hub into the mix just disconnect one of the 3 computers connected to the old hub and plug it into the new one, then connect a cable from the new hubs uplink port to the place you removed the old computers cable from.
ie:
Old Hub:
Port 1
Computer
Port 2
Computer
Port 3
New Hub
Port 4 Nothing
UPLINK
DSL connection
New Hub
Port 1
Computer that used to be in Port 3 of the old hub
Port 2
Whatever
Port 3
Whatever
UPLINK
Connected to Port 3 of old hub
I tried to be very descriptive, the boards pretty dead. Note it doesn't matter how many ports the new hub has I only went to 3 you can go to whatever.
Anyway, right now you have 4 ports on your hub, your uplinks taken because of the DSL modem and you cant connect the 4th port because its a rule of hubs.. just going over everything, now the other 3 ports are used.. if you want to add another hub into the mix just disconnect one of the 3 computers connected to the old hub and plug it into the new one, then connect a cable from the new hubs uplink port to the place you removed the old computers cable from.
ie:
Old Hub:
Port 1
Computer
Port 2
Computer
Port 3
New Hub
Port 4 Nothing
UPLINK
DSL connection
New Hub
Port 1
Computer that used to be in Port 3 of the old hub
Port 2
Whatever
Port 3
Whatever
UPLINK
Connected to Port 3 of old hub