What are the requirements for a nomination made by a policyholder to be effective, and how can it be changed according to the Insurance Act?

Section 39. Nomination by policyholder(2) Any such nomination in order to be effectual shall, unless it is incorporated in the text of the policy itself, be made by an endorsement on the policy communicated to the insurer and registered by him in the records relating to the policy and any such nomination may at any time before the policy matures for payment be cancelled or changed by an endorsement or a further endorsement or a will, as the case may be, but unless notice in writing of any such cancellation or change has been delivered to the insurer, the insurer shall not be liable for any payment under the policy made bona fide by him to a nominee mentioned in the text of the policy or registered in records of the insurer.