in the bios config menu, you can access it when you start up your computer and spam the appropriate keyboard key, you can find out which key it is by the brand of the computer, or the brand of the motherboard if you assembled the pc yourself, then inside the bios config menu you will find the secure boot option.

for example, on my computer, I need to turn it off completely, then press the power button and quickly press the f2 key repeatidely, then instead of launching my operating system, it launches the bios config menu, and in that menu, under the “boot” section, I find a line called “secure boot” which I can enable and disable, once i’ve done so, I press f10 to save the configs I made, and boot my system where I want