When you insert a USB flash drive into the USB port of your Apple computer, Mac OS X automatically reads the contents of the flash drive. It may then display a window showing the contents of the USB flash drive. If this doesn't happen, you can find the USB flash drive quickly by looking in the Finder and viewing the devices connected to your computer.
Open the Finder.
Find the word "Devices" in the upper-left side of the Finder window. If your USB flash drive has been correctly inserted, there will be a temporary drive icon labeled with the name of your USB flash drive. Temporary drive icons are white, while permanent drive icons, such as the icon for your hard drive, are gray.
Double-click on this icon to view the contents of your USB flash drive.