Apparently it does have the ability to unlock cores. Johan, where did you get that manual. Manuals library? Is that free?
Anyway, zoran, the feature to enable core unlocking is called Advanced Clock Calibration or ACC. You must have it enabled.
Please realize that not all CPUs with disabled cores will have viable cores to unlock. If they are too far out of spec it just won't work. Or maybe one out of two will unlock successfully but the other core will not.