Which way are you trying to send a file?
Phone to pc? Or pc to phone?
You need to make the target 'discoverable' and search from the 'source' to make a 'pair' with the target. Then find the file you want to send,(right-click) send...via..bluetooth and it will transfer.
It might be easier to get a USB cable to join phone to pc USB port.
Then open two explorer windows, and drag and drop the files across, (or copy & paste).
* Does the pc have bluetooth built-in?