[ English ] Network configuration (DHCP) - Mac OS X 10.5 (Leopard), 10.6 (Snow Leopard)

Find "System Preferences" icon in your dock and click on it.

OR:  Select  "System Preferences" from the "Apple menu"

In "System Preferences", select  "Network".

On left there are multiple choices of network cards. Click on "Ethernet".
From the "Configure:" dropdown menu, choose "Using DHCP", then click "Apply" *

NB! You may not be able to change your configuration if your network cable is connected.
In that case, unplug the cable, make the changes and re-plug it.