Hi Damien,
There is a pretty good guide at the following location;
http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html
I'm guessing from your brief description you wish to extend the internal wireless AP found inside the UC5X0W series.
You would need a TNC patch cable and appropriate antenna that worked in the 2.4Ghz frequency range.
eg. Maybe 20' patch cable p/n AIR-CAB020LL-R and maybe with a p/n AIR-ANT2485P-R patch antenna.
But, please choose the appropriate cable length and appropriate antenna to meet your customers needs.
regards Dave