Hi user402 ! It's very simple .You will update from your SDcard folowwing the steps below:
1-download on your PC the Update file in format .zip
2-connect your phone to PC with the cable(you must have installed on PC the driver for Nokia3)
3-copy the file in zip format to the SDcard at the root of Sdcard
4-disconnect the phone from PC
5-put your phone into Recovery menu using the buttons
6-from the menu choose with vol-up or down "Apply update from SDcard"
7-navigate to the file you copyed before from PC and hit ok
All the best !