Ok,
press [UTILITY]
Press cursor < > until you get to "SYS" then press enter.
press cursor < > until you get to "Onbrd Mic"
rotate the TIME/VALUE dial to off
press [UTILITY] to exit back to the play screen
Select [MIC] as your input source and connect your external microphone to the XLR input.
These instructions are from page 32 of the owners manual.
http://www.rolandus.com/product_manu...oadId=MjI1Nzcw
It looks like it doesn't provide phantom power. If your microphone requires phantom power it won't work without an external power supply.
-Rav