Hi Fabio,
The turntables connected to the inputs on the back of the DDJ, with the switches set to PHONO. The DDJ inputs should be set to USB on the channels.
If you have the DDJ configured as your audio device and DVS mode enabled in the preferences, you should then see the green circles appearing on the scopes with the rekordbox DVS timecode playing.
Can you please confirm that and let us know what shows on those preferences pages if not? Thanks!