Can you confirm that you really have the board you say you have : LPCXpresso board for LPC1769 with CMSIS DAP probe|NXP ?
The above board should not provide an mbed type interface.
If you have a different board that does have an mbed type interface, then the problem may well be that you have not installed the mbed serial port driver (assuming you are using a Windows PC). If you don't do this, then the debug interface will not be visible either. You can get the mbed serial port driver installer from: Windows serial configuration - Handbook | Mbed
As an aside - if you are only just starting out, then you may wish to consider the MCUXpresso IDE rather than the older LPCXpresso IDE product. For more details, visit http://www.nxp.com/mcuxpresso/ide
Regards,
LPCXpresso Support