I have just transferred over from uTorrent (I was getting tired of the SPAM! ) Anyway, a feature I liked from that was that I could download a .torrent file as to be opened after finishing being downloaded - or just opening a .torrent file already in my system - and uTorrent would pop up a dialog window giving me the option to choose the files in the .torrent file to download. qBitTorrent does not seem to do it like this.
That is nothing to do with qBitTorrent, you need to set the file associations in your operating system, and to get it to open when you download a torrent you need to set your browser to send it to qBitTorrent.
Tools->Options...->Behavior
Towards the end there are 2 checkboxes for associating qBittorrent with .torrent files and magnet links. Enable them.
NOTE: The checkboxes don't stay enabled then you need to do this. Launch qbt with admin rights. Go into Options and enabled them. Then exit qbt and launch it with normal rights. It should now work.