Secure boot – How to append custom certificate to db if BIOS has no such option?

I have HP 245G7 notebook. The BIOS is very basic and there does not seem to be any option from within to append my own custom certificate to db database of secure boot.

If there is an option in this model, I would like to know.

I read somewhere that only HP business laptops have such an option. When I call HP support they say HP245G7 is a business laptop.
Given that and assuming that BIOS does not have such option, what are alternatives to append my own certificate (.cer file) to the db database?

Certificate is created on Windows using powershell command New-SelfSignedCertificate