If they all have IP addresses in the same subnet (and assuming there's nothing fancy like VLAN's on the switch) then they'll be able to 'see' each other. You can check this with the ping command. Open command prompt on PC1 and type 'ping PC4' and hit Enter. You should see 4 'Reply from...' lines, which shows at a low level the computers can see each other. You can then of course ping PC0, and then try a similar thing from your other two computers to figure out which computer can see which others.
If any of these ping tests don't get a reply then double-check IP address and subnet mask settings on each PC, maybe try replacing the network cables and change switch ports, and also disable antivirus and firewall software temporarily as these can stop ping from working.
If all the pings get a response but you cannot see the file shares on the other computers then you need to look at your sharing options. Make sure file sharing is turned on, that services (like Computer Browser) are turned on, and ensure that the file and share level permissions are set correctly.
