Time-sheets can be found in the Upstack client portal.
The Upstack developer portal allows developers to keep daily hours recorded and also asks for high level updates regarding the stories/features/functionalities etc. that they have been working on.
Once your project starts, your Upstack Account Manager shall set your project up on the company portal, and the time-sheets functionality will start being populated with high level updates related to hours worked and work conducted by your developer.
As a client, you can view the information logged, using your credentials provided, directly on the Upstack portal.