How to Flash Xperia Using Flash Tool via USB

• Download the flash tool from the link provided at the bottom of this post
• Unzip the file and run setup
• During the installation, remember the path where the software is installed. Generally, the path for 64 bit windows will be “C:\Program Files (x86)\Sony Mobile\Emma\” and for 32 bit, it will be “C:\Program Files\Sony Mobile\Emma\”
• In unzipped folder (you have downloaded), there will be a customization .ini file. Copy the file and paste it into the installation directory
• After copying the file, launch Emma software from start menu
• Connect a USB cable to your phone and then to your PC. The phone should be turned off while you connecting it
• While connecting the phone, hold down flashing key. For most phones, the flashing key is volume down key. But it varies from model to model. For a complete list of phones, visit this page to view the key and other details 
• After you press the flash key, the tool will detect your phone and will list the suitable software for it automatically
• Select the software from Service list and click on Apply Service option
• Your phone will be flashed