Using the Device Notifier - click on the device name and you will be shown relevant options, one of which will be Open with File Manager. This opens Dolphin with the contents of the device listed.
Mounting in Dolphin - if you already have Dolphin open you will see the new device appear in the Places panel. Click on that and you will see the contents of the device.
If you prefer the drive to be automatically mounted, you can now do this by going to System Settings -> Hardware Section -> Removable Devices and check Enable automatic mounting of removable storage media.
