How do I create an invoice?

In order to create a new invoice, you need to go to Accounting → Invoices → Add invoice. You can add items manually to the invoice by inserting new rows or by clicking on the Add outstanding time/costs and select from the dropdown: 

•  Add from Timesheet – creates an invoice based on tracked time
•  Add from Expenses – adds expenses to the invoice, but make sure they have the same currency as the invoices.
•  Add from Projects – creates an invoice based on flat-rate projects
•  Add from Tasks – creates an invoice based on flat-rate tasks

NOTE: If you select Add from Timesheet, there's the option to attach a time report to the invoice to offer more details about what you've been working on. 

You can also create an invoice by going to Projects → Select a project → Overview → Click on Invoice Unbilled AR.