How To Share Internet Connection Using Ethernet Switch

Im having a ACT Broadband internet connection, he provides internet connection through a wire which runs into my room that can be directly connected to the my computers NIC. Whenever i switch on my computer and opens the browser it first redirects to the page url... where it asks for Username & Password, our ISP gives us a IP Address which displays on the web page after logging in.I want the internet connection to be shared with my roommates so i bought a 8 port Ethernet switch (url..), which is having a uplink port also. I have connected the wire given by the ISP to the up link port of the switch & i connected my PC to one port of the switch with another network cable. I also connected my friends PC to second port of switch with another network cable, my problem is that when i sign into my ISP web page and start using the internet & my friend also wants internet in his PC & when he opens the browser the ISP's webpage is appearing and when he sign's in internet is disconnecting in my Pc. I tried to change the IP but as a default IP is given by the ISP if change the IP internet is not working.