If you turn off Automatic Software Updates in Settings > System, new versions will not be downloaded to the handset automatically. In that case you have to manually.
1. To access the system menus, hold down the top button for a long time.
2. Select Start/Stop from the Settings menu.
3. Select System from the drop-down option and scroll to the bottom.
4. You'll see the version (e.g., v4.60), the option to Install Now
5. To confirm, press choose.