Claim authorization is the act that the insured or beneficiary authorizes others to handle claims on behalf of others. It is not filled in by the salesman or the insured, but by the beneficiary.

if you are the insured and the insured/beneficiary, then you should sign it. You can entrust a salesman to handle it for you, then the client will fill in the name of the salesman.

Further reading: How to buy insurance, which is better, and teach you how to avoid these "pits" of insurance.