Plug it in!
I can speak for Ubuntu that (by default) it will show up automatically on your desktop and even open a window to show you what's on the USB drive. You'll have (again, by default) read and write access to the device.
It pretty much "Just Works(tm)".
Last Wiki Answer Submitted: June 6, 2011 3:17 pm by Koohiisan4,990 pts.
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I think you are asking because the system is not recognizing the usb drive.
Login as root and execute fdisk command to see your devices and look at the usb drive.
Assuming your usb drive is the /dev/sdb1 device create a mount point like this
Then you can mount the drive executing the following command:
vfat is the filesystem of the usb drive.
Tell us if you have troubles.
Regards.