In the case of Turkish and Iranian Kurdistan, you get VISAS to those nations and then proceed to go to the Kurdish-majority regions.

In the case of Iraqi Kurdistan, you get a special VISA to visit Iraqi Kurdistan from the Iraqi Embassy or upon arrival in Iraqi Kurdistan (if you are a national from certain countries and are arriving in Iraqi Kurdistan from somewhere other than Iraq).

In the case of Syrian Kurdistan, it is currently STRONGLY discouraged to go to Syrian Kurdistan. Although it is among the safest areas in Syria, that is not saying much.