There are two scenario here :

1)     You claim after the incident happened – such as accident,

2)     You claim before the incident happened- such as Critical illness

In both cases, if your insurance policy purchase through an insurance broker, call the broker immediately, they will assists you in making all necessary arrangement.

If you fail to locate the person, please call the customer service of your insurance company for help.

In most cases, you need to fill up a claim form and submitted together with proof to sustain your claim ( Medical Bill, Medical Report etc )

A very important note for all insurance policy holder, please inform your family members or dependants about the insurance policy that you purchased.  Just in case anything happened to you, you might not even have the opportunity to inform them about the insurance policy that you had. If that is the case, they will not able to enjoy all the compensation since no one is making the claim on behalf of you.