Instructions
Launch the Dolphin Emulator application on your computer by double-clicking on the icon on your desktop. If the icon is not on your desktop, click on the "Start" button in the bottom-left corner of the screen and select "All Programs" from the slide-up menu. Find the Dolphin Emulator application and select it.
Click on the "Tool" tab at the top of the window and select the "Memcard Manager (GS)" option from the drop-down menu.
Click on the "Browse" button near the left-hand side of the configuration window. Find the folder you want to serve as the Dolphin Emulator application's memory card. Press the "OK" button once you are done making your selection.