Tap the GEAR icon (bottom of the app). If your Core is connected and the firmware is up to date, you'll see a "Firmware up to date" message. If you do in fact have a firmware update available, select the Core in the app, and "Update Firmware."
Pro Tip: If you have trouble updating your firmware, try updating while the Core is OFF the charger and outside of the garment which usually does the trick!
If your firmware update fails or gets stuck during the update, try force closing the app and reopening it. You should then be able to restart the update. If the issue persists, please contact Support for further assistance.