how to join video with hjsplit -- please!

Please someone help me. I'm really desperate :/

I'm using hjsplit and I want to join parts of movie. There's a not:

"To join a set of files, please first open the .001 file using the 'Input file button'. If the other files are in the same directory they will be found automatically."

All files are in the same directory, they have the same name with extension .001, .002 etc.
BUT WHEN I OPEN THE .001 FILE AND CLICK START, THE RESULT IS THE SAME .001 FILE... IT DOESN'T JOIN

Please please please anyone can help me?
Thank you so much!