Second map on SD for nuvi 255w

this is for the moderators!! i have a 255w that i updated last week an on the update it was written like this

[I]Changes made from version 7.50 to 7.60:

Added support for a second map on an SD card.
Improved route calculation logic.
Fixed an error that sometimes caused water map features to not appear on the turn list.
Fixed an error that caused the device to find no results when the user changed state or province during address searches (2010 maps only).
Fixed an error that caused the device to not find streets that were spelled with a diacritic ß, instead of ss.[/I]


now my question is how to put a second map on an SD CARD (how to rename it )??? THNX

SD:\garmin\gmapsupp.img on SD one name recognized
SD:\garmin\gmapsup1.img on SD other name recognized