By installing this module, you will find an option "Import Account Invoice line from Excel file?" under Settings >> Configuration >> Invoicing menu. If you select that option and click on "Apply" button in settings, then you will see option "Import/Export Invoice lines" in "More" section at the top bar in Invoice form view.
Sometimes user includes 12 (dozen) Qty by default in their orders to suppliers. In this kind of cases they just need to know the product code from ERP system. With keeping this case in consideration, we made our module so simple specially for users so that if they add only Code in excel file then system will take default Qty automatically from settings. So there is no need to even provide Qty while importing file. In order to set default Qty, user need to go to Settings > Configuration > Purchases menu, find the key "Set Default Quantity" and set the value as per their requirement.