Click the "Auto Match" button. The tool will scan the filename of your video and search for subtitle hashes online (via OpenSubtitles or JAV-specific databases).
Download the Javsub_Portable.zip file. Extract it to D:\PortableApps\JavsubTools\ . You will see an .exe or a .bat / .py script. javsub portable
If the auto-match fails, use the slider or numeric input to shift the subtitle. Most JAVs need a delay between -3000ms and +5000ms . Click "Preview" to see the change instantly. Click the "Auto Match" button