I normally recommend SelfSSL7 but I was looking at Let's Encrypt which generates free CA SSL certificates.
This is in the context of Windows, specifically IIS SSL or securing ADFS.
To do this you need a client and one of the browser clients on the list was ZeroSSL.
If you click the Tools button, you'll see a "Self-Signed Certificate Generator".
There's a private key and a certificate.
Save the two files somewhere. If you save the certificate as a .cer file, you can double click on it and get the certificate wizard. You'll note that it has no private key which makes it useless for SSL. The certificate is valid for a year.
Now use OpenSSL to run:
openssl pkcs12 -export -out c:\xxx\adfs.pfx -inkey c:\xxx\zerossl.prv -in c:\xxx\zerossl.cer
Loading 'screen' into random state - done
Enter Export Password:
Verifying - Enter Export Password:
You'll need to pick a password.
Now if you double click on the .pfx file, the Import wizard will guide you as to installing it into the certificate store. You'll need to type in the password.
If you look at the "Enhanced Key Usage", you'll see it covers a lot of cases which is cool.