Display Total Value of Account in SalesForce

When creating an opportunity you can add products , along with it's sale price. Now, when the opportunity has been won that value need to be added to the account value automatically. To do this you need to do the following:

• In Sales Force go to Setup > Customize > Accounts > Fields > New;
• Select Rollup Summary as the type;
• Choose Sum as the action;
• Select Filed to Aggregate: Amount;
• Then Filter Criteria 'Only records meeting certain criteria should be included in the calculation';
• And 'Won equal TRUE';