Step 1: Enable USB debugging on your device. Navigate to Settings > Development Option > USB Debugging and toggle it on.
Step 2: Connect the device to the computer and copy the downloaded ROM and Gapps files to the root of an external SD card installed in the device. In case you don’t have access to an external SD card, you can copy the files to the root of your device’s internal SD card, however you won’t be able to do a complete wipe as detailed below. Skip the complete wipe if you don’t have a MicroSD card.
Step 3: Once the files have been successfully copied, you’ll need to boot into Recovery Mode to wipe your device and then install the ROM. To do this, power off your Galaxy S4. Now, hold the Home + Volume Up buttons and power up the device. Once the screen turns on, let go of all the buttons.
Step 4: Using the recovery, you can create a unified Nandroid backup of your device, which is basically a snapshot of your current installation. If you have a Micro SD card handy, create the backup on the card so that your backup is stored outside of the device. To create the backup, go to the Backup and Restore menu in the recovery and create a new backup.
Step 5: Once the backup is completed, do a complete data wipe of your device to start anew. Then, navigate to Wipe and select Wipe Data/Factory Reset from the Recovery.
Step 6: With all that sorted, you’re now ready to commence the installation of the custom ROM. Navigate to the Install menu and select the Resurrection Remix ROM file. Commence the installation. The installation process will take 5-10 minutes.
Step 7: Once the installation is complete, navigate to the Install menu and select the Gapps ZIP file and flash it. Now, reboot your device to experience Android 6.0.1 Marshmallow.
And that’s it. The first boot may take a while, so don’t fret. Once the phone boots up, you’ll be presented with the initial Setup menu for Marshmallow. Once you complete the required steps, you’ll be taken to the Android Marshmallow home screen. Enjoy!
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