You might refer to the below topic link, hope it helps:
Some web forms contains file upload boxes that allow users to upload files to a website. File upload boxes cannot be manipulated by scripting, so they need to be processed differently than other web form input boxes.
Follow these steps to add a file upload FormField to your project.
- Select the file upload input box in the web browser and add a FormField content element to your project.
- Enter the path of the file you want to upload in the Capture window. You can also load file paths from an input data source.
- Set the FormField option "File upload" to true in the advanced options tab.
A web form that uploads files cannot be submitted to a new browser window, so such web forms will always open in the current browser window.