Sorry! Saw to late but there is twa ways.
1] Using Nokia PC suit
a) Run PC suit and select programs to install.
b) Double click on .sis file and PC suit will ask if you want to install (quick)
2] Load the sis file in Nokia folder direct and from Nokia run the install .sis file or use the Applications manager.
Once you are set you must try the Garmin GPS routing software, It rocks!