Run torn without arguments for a synopsis. Use -h for a complete help.
In order to use it with flameshot: 1. Place torn somewhere where it can be executed (i.e. ~/bin or /usr/local/bin) 2. Place torn.desktop to ~/.local/share/applications/ 3. (optional) Place torn.png to your application-icon directory (e.g. ~/.icons//256x256/apps or /usr/share/icons/Adwaita/256x256/apps/ or …)