CertCentral is not a Certificate Authority, it does not issue or sign anything. You must have a valid Code Signing certificate in the CurrentUser\Personal store.

How to generate a Self Signed Certificate.

There are multiple tools available: powershell, makecert, Azure KeyVault, openssl and more.

    New-SelfSignedCertificate -Subject "CN=Joey, O=Ramones, L=Queens, S=NewYork, C=US" `
    -FriendlyName Joey `
    -Type CodeSigning `
    -KeyUsage DigitalSignature `
    -KeyLength 2048 `
    -KeyAlgorithm RSA `
    -HashAlgorithm SHA256 `
    -TextExtension @('{text}', '{text}Subject Type:End Entity') `
    -Provider "Microsoft Enhanced RSA and AES Cryptographic Provider" `
    -CertStoreLocation "Cert:\CurrentUser\My"

Login with a GitHub account

Once you are logged in you will get access to your API key, required to authenticate the CLI