The network has to go Modem-----> Router ------> Switch. The physical location of the devices doesn't really matter as long as they are connected in that order.
For example if your Router is in Room A, and your modem and switch are in Room B, You would have to have two Cat 5/6 cables that ran from Room A to Room B. Cable 1 would connect the modem to the router and cable 2 would connect the router to the switch. It's the same concept as if they were in the same room right next to each other, you just have longer cable runs.
I have the same setup in my apartment here in Korea. The Apartment is pre-wired, but where the switch location is next to the front door in the entryway, at the other end of the apartment from where the computers are. Luckily every room had two drops, so I just had to move one cable from the switch to the modem.
This is the guide
I used when I wired my house
back in the states, a few years ago. It should give you some good ideas.