On your phone: Go to Settings > Developer Options > USB Debugging . If you don’t see Developer Options, go to About Phone and tap Build Number 7 times.
You need (Windows) to flash a custom recovery first. For Mac users, use Heimdall. gti9100 firmware 511 download upd
Modifying your device's firmware voids any remaining warranty (none for this device anyway) and carries a risk of bricking your phone. The author and sources mentioned are not responsible for any damage to your device. Proceed at your own risk. Always verify checksums (MD5) of downloaded files to ensure integrity. On your phone: Go to Settings > Developer