HI
I have a phone type sony ericsson
How can I decode it because it is code on it and I can not turn it on

Are you referring to the lock code? The default lock code on some phones is the last 4 digits of your phone number.

If it doesn't work... let us know
I have a few ideas...

There is an app called XS++ that can do a code reset.. but this is all up to u to learn how to use the app... these programs can screw up your phone if not used correctly.