how to configure using modem,rourter,hub....and the pc is more than 25

Are you using server software?
You will need to configure the security policies on the server for each of the clients.

If you are just setting up an open network then you should be able to set up modem then router then connect the switch(s)(Hub) then connect each client to the hub and the router should distribute IP addresses to each one connected for automated connectivity. If there is an issue then do an ipconfig /release and renew for each client to establish an ip address.