@Ennahli
I translated your message. Kindly post your future questions/feedbacks in English so we can assist you, this is an English based forum.
In order to use the fingerprint as a lockscreen security option, you must first set a primary security method like a pattern, PIN, or password.
PS: US models of Xperia phones do not have Fingerprint option activated out of the box, in case you have your phone imported.
