Most BLU devices use the SP Flash Tool . You would load the "Scatter" file from the extracted folder into the tool.
Ensure the MediaTek (MTK) or relevant USB drivers are installed on your PC. BLU.1306720WRZ.rar
Flashing the wrong firmware can permanently damage ("hard brick") your phone. Always double-check that your specific model number matches the one intended for this file before proceeding. Most BLU devices use the SP Flash Tool