Software Download Link- Primo C4 Firmware
Step 1:Install the drivers.
Step 2: Open Flash Tool
Step 5: Connect The Handset After clicking the "Start", press the volume down key of your handset, and connect it to your computer with USB cable. Remember: Before connecting the handset with your computer, you must turn it off. Also notice that the battery has to be kept inserted. Flash operation will begin, you will see this window: