You can only enable this setting in the BIOS
If you dont know your BIOS password, but you can get to your motherboard you may be able to reset the password or, a more brutal option, reset your BIOS.
Power down your machine before attempting these!
Depending on your board there are ways of reseting the password, some involve removing a small plastic tab, others have switches or jumpers. Consult your motherboard manufactuer for this.
If you have no other special settings in the BIOS removal of the small watch battery on the board for around 5-10 minutes, then re-inserting will reset the BIOS to factory defaults (The internal clock will be wiped and you will need to set this again too), This will clear your BIOS password and you will be able to change the virtualisation setting.
Note: Depending on your computer make/model, you may not have this style of BIOS battery. You should consult the user manual, or the service manual for your make/model to locate and determine if the CMOS/BIOS battery is of the removable kind.
Perhaps check out this other existing SU question:
(OP's laptop model was discerned from another, related question posted by the same OP)