There are possibly two claims forms to investigate.
For loss of goods there is a damage claim form. You need to note down the items lost and the rough cost of these.
If it was in addition out for more than 12 hours, there is the extended outage payment scheme form. This is the standard payment of $80.00.
Also, it is worth noting in the the event that a claim is unsuccessful with Western Power and you want to apply to your insurance, your insurance company will want confirmation from Western Power that a recorded outage occurred on that date. Either way you will need to go through the claims process. The links are here: