Have you got a floppy disk icon on the desktop? If so, you should be able to put a disk in the drive then double-click the icon to mount the disk and display its contents in a file manager.
If you haven't got a floppy disk icon, then right-click the desktop and select Create New --> Link to Device --> Floppy Device. This will create the desktop icon, and you can then mount it as above.
USB devices should be detected automatically, and depending on the distro may create a desktop icon as above, or may pop up a dialog asking you what you want to do.