To enable virtualisation in the BIOS of the Gigabyte Z790 AERO G motherboard, you can follow the steps below:

Start the computer and press the "Del" key to enter the BIOS. 2.
Navigate to the "Advanced" tab using the arrow keys. 3.
Select "CPU Configuration" and press Enter. 4.
Look for the option "Intel Virtualization Technology" or "Intel VT-x" and make sure it is set to "Enabled". Please note that the exact name and location of this option in the BIOS may vary depending on the BIOS version. 5.
Save the changes and exit the BIOS.
After enabling virtualisation in the BIOS, you can use virtualisation software such as VirtualBox or VMware to create and run virtual machines on the computer.