STEP 1: Plug in Network Cable: Plug one end of your network cable into the Mac's Ethernet jack and the other end into the network jack on your wall.

STEP 2: System Preferences: Go to the Apple Menu and choose System Preferences. Click the Network icon.

STEP 3: Configure Network

For Configure, choose "Built-in Ethernet."
Click the TCP/IP tab.
For Configure, choose "Using DHCP."
Click the Save button.
Close the System Preferences by clicking the red button in the upper left of the window's title bar.