You can add subtitles to your Youtube videos, just online, you don't need to download any software
Select a YouTube video pasting the complete url in the apposite place and click "LOAD"
Use the "START" and "END" button to get the begin and start time
Press "ADD" to store the current subtitle
With "NEXT" the counter and the timecode will increase automatically.
Use the quick notes to set some words (like names or something)
From the Notes text area you can select and copy some annotations about the video's dialogs
Once you have written the subtitles press "CREATE SRT FILE" to download the file.