Here is a nice thread: Xperia Miro (and Tipo) Flashing for dummies. How to flash any ROM.
And here you can find official TFT files for flashing: ***Xperia Miro (Mesona) - ST23i/a Official Firmware Files***
If you have further questions or need detailed help for your device, please check the Xperia Miro, Tipo (Dual), J, E General forum.
Questions for your device should be posted in the Xperia Miro, Tipo (Dual), J, E Q&A, Help & Troubleshooting section.