The PIN code and SO PIN code can be changed using the Smart Security Interface (Windows) or SecureDoc2 (MacOS) application. More details can be found in the instruction available here -

ATTENTION! We recommend that you stick to the default SO PIN code and keep the secure envelope in which it was provided. If the PIN code is locked, without the SO PIN code, it will not be possible to unlock the PIN code. In this case, it will be necessary to purchase a new certificate with a cryptographic card.