Depends, chances are linux has recognised it already. Do you have any other ethernet cards or chipsets? Linux recognises ethernet interfaces as ethX
starting from 0. Assuming you already have only one, run these as root to bring up the second one.
ifconfig eth1 up <static ip>
# if you use DHCP then don't put an IP in the above command and run this
dhcpcd -d eth1
As is obvious with this answer, if you provide more info then we can provide much more specific answers.