You need to plugin the USB, and read the doc and code.

Dependencies:   USBHost mbed

Fork of USBHostMSD_HelloWorld by Samuel Mokrani

Revision:
5:fc580cab6a61
Parent:
3:17ca010bda2e
Child:
6:a801dcc9ff68
--- a/USBHost.lib	Wed Mar 13 10:30:25 2013 +0000
+++ b/USBHost.lib	Wed Mar 13 15:50:06 2013 +0000
@@ -1,1 +1,1 @@
-https://mbed.org/users/mbed_official/code/USBHost/#e48791a1ef18
+https://mbed.org/users/mbed_official/code/USBHost/#1571e517a91b