It’s not possible to convert an accepted estimate into a new project in Harvest. A project has a specific data set—project type, project budget, billable and non-billable tasks, and certain teammates, for example. The data entered on an estimate, however, is completely free-form and isn't tied specifically to information that's found within a project's settings. Because of that, there isn't a clear connection for turning an estimate into a project. 

You can, however, create an invoice from an accepted estimate by clicking the New invoice button to the top right of your estimate. Invoices created this way will be linked to your client but not to a project.