Instructions
Click the "Start" button and select the "Computer" option. Double-click on your computer's default storage drive and double-click the "Program Files" folder.
Double-click the "PCSX2" folder, followed by the "Plugins" folder. Drag the DEV9ghz plug-in file into the PCSX2 folder. If you do not already have this plug-in downloaded, you can download it from the official PCSX2 forums.
Double-click the PCSX2 icon to launch the program. Click the "Config" menu and select the "Plugin/BIOS Selector" option.
Click the "Plugins" icon, followed by the arrow to the right of the "DEV9" heading. Select the "DEV9ghz" option from the drop-down menu.
Click the "Apply" button followed by the "OK" button to save the changes. Now, when you launch a game that has online capabilities, the PCSX2 program will be connected to the Internet.