There are a couple of things you need to set up before you can start creating and transfering invoices.
Go to "Invoice" in the main menu, choose a time intervall you wish to invoice for and click on "+ Create new invoice" at the top right corner. After matching approved time reports with your invoice agreement the system will generate invoices which you can review by clicking on "Show invoice rows". Then click on "Save invoice" to save one invoice or "Create all" to save all of the automatically generated invoices.
After saving you can edit the contents of every invoice by clicking on them. Just don't forget to save your changes.
By default your invoices will be saved on today's date, that is, the date you have created them.
To transfer one invoice click on it and scroll until you see "Transfers". In that section click on a button called "Send to..." (the name will vary depending on the invoicing system).
To transfer more than one invoice, choose the invoices you want to transfer, click on "Transfers" and choose "Transfer to..." (the name will vary depending on the invoicing system).
Status of your transfer(-s) is visible in the page "Invoice".