How do I enter my code into my peugeot 405 radio,?

I have the code to my radio but it has been entered wrong & now says security, It will not allow me to do any thing but if i hold the band disc button & swicth the radio off & then back on it will come on for about three minuites & it bleeps & then it shuts down & says security again. The make of radio is clarion & came as standard in my peugeot 405 executive.

Any help or advice would be most welcome & thanks in advance to any one that helps.