For the "File to Upload", you can use the "Browse" button to find the file on your system or you can type the full file path directly in the box.The "Filename at site" can be used to give the file a different name when it is uploaded to the host. The default is the same name as the original file, so you don't need to enter anything if the uploaded file does not need to be renamed.
If you check the "Overwrite existing file" box, then the previous version of the file on the host (if any) will be overwritten with the uploaded file. If you check the "Save existing file.BAK" box, then the previous version of the file (if any) will be renamed with an added ".bak" extension. (The .BAK version can be restored using the form below.) If you do not check either of these boxes, the default is "New file", and the upload will fail if a file with that name already exists.
After selecting a file to upload and entering any options you need, click the "Upload File" button.