What is the PIN you are asking for?

There may be three cases:There may be three cases: 

1. If you ask for the PIN when trying to install a P12 or PFX file, this is the transport PIN that you must have provided the Certification Services Provider to which you have acquired the digital certificate. If you do not know this PIN, get in touch with them.

2. If you already installed your digital certificate in software and it is asking for your PIN when trying to digitally sign, that is the PIN that you defined when installing the P12 or PFX file.
3. In the case that you have a cryptographic token or card, it is the PIN that protects the device. You also have to provide it with the device.