To use the Expense forms, the Mobile Time Tracker app license should be enabled with the Expenses feature for your org.

To configure the Expense screen, go to TT Apps tab in Salesforce, and click on the App Key name to configure it. Click the Config button and go to Expenses, enable the Expense Tracking check box, enter the Expense Form label, and add additional fields, and make the additional field mandatory or non-mandatory and click the Save button to save the changes.