1. Click Settings, click Customizations, and then click Customize the System.
2. In the Default Solution, under Components, expand Entities, and then expand Opportunity.
3. Click Fields.
4. Locate and double click on the Revenue field (isrevenuesystemcalculated).
5. Under Type, change the Default Value setting from User Provided to System Calculated.
6. Click Save and Close.
7. In the Default Solution, click Opportunity.
8. Click Publish.