Linux Lite is using standard Ubuntu repositories, and qBittorrent is not part of it. So we have to add additional repository and then install qBittorrent client from it.

Adding qBittorrent repository

$ sudo add-apt-repository ppa:qbittorrent-team/qbittorrent-stable

Then update the repo:

$ sudo apt-get update

and then install qBittorrent:

Installing qBittorrent client

Run following command in terminal:

$ sudo apt-get install qbittorrent

Now qBittorrent with GUI is installed on your system and you can start it directly from your system's Main Menu.