This video shows how to select a file or multiple files to convert.
For this example, we will use the Transactions app, but for other apps, the process and the selection are similar, as well. Let's start the app, read the welcome message.
When you start the app, it automatically opens the file selection form, so, all you have to do - is just select the file. You can change the folder. The default folder is the Downloads folder, where you usually download your transaction files, and then you would simply click a file. You can change the folder, navigate to a different folder if you have files in the different folders.
If you like to select multiple files, then you would have to click one file, then hold the 'Ctrl' button. The process on macOS is similar, you just have to hold the command button, so you hold the 'Ctrl' command button, then click the second file, and so on.
If you would like to select several files - you can do that, as well, by drawing the rectangle with your mouse, so, you click the left button and hold the left button, and then drag the mouse - and you see the files starting to select. This is a standard way of selecting files, and this is standard file selection form on Windows, so there's nothing specific about using in this software, compared to other software like Excel, selecting Excel files in Excel or Microsoft Word, or things like that.
In most cases, you would need to convert one file, so, select the file and click 'Open' and the file is open now.