Call your insurance agent or company right away, and be sure to ask questions. See if you are covered for the loss, and if the claim is more than your deductible. Ask how long it will take to process your claim and what other steps you should take to get payment for the loss. Advice from a good agent can help. However, you should still read your policy yourself and take the steps outlined there.
Most insurance companies require that claims be in writing and made promptly to the agent.
Even if this is not stated clearly in your policy, it is smart to follow up a telephone call to your agent with a written explanation of what happened. Your agent may tell you to make temporary repairs or take other steps to protect your property from further damage. Save the receipts for what you spend and give these to your insurance company for reimbursement. If you have to live somewhere else while your property is being repaired, keep all receipts for expenses such as food or hotel bills. Make a list of lost or damaged items.