I installed the Sygic program from ovi and then connected the n900 to pc, but unfortunately I couldn't find the sygic folder on my phone. I tried copying the folders to the memory card, but the sygic program couldn't find them.
It should be noted that Sygic's folder is /home/opt/sygic/ (At least on my phone), so you should put the Maps and Res folders there (Also, it's capitalized as "Maps" and "Res", but I haven't tested if Sygic is case sensitive).