Updating garmin nuvi 255

hello i have just downloaded maps city navigator Europe 2012.20 for garmin satnav.
can anyone tell me how to get the updated maps onto sat nav please.
i have it connected to PC but have no idea what to do next
many thanks
Answer #1
would this help?
http://www.haklabs.com/2010/garmin-2011-gps-update/
not sure if its related but found that tutorial on google