That depends on which install method you used:
a) If the system is running a correctly configured manual HDD install, like that posted by @elfnino, then your system should auto update if updates are enabled in the MyOSMC menus
b) If you did an old HDD install that requires the USB stick to still be inserted or is running from the USB stick, and your local media files are on the network or an external device, you should simply be able to:
- backup your system settings to an external device, using the MyOSMC addon
- reinstall with the upcoming installer
- restore your settings from backup.