Put it in your path. You can figure out your path by running:
/usr/local/bin, if it's in your path, would be the place to put it so everyone could use it. I keep programs I write for my own use in my own bin directory and put $HOME/bin in my path. I think 'path.sh' is a bad name for a program that runs qutebrowser - how about 'qute' instead? Then you can run qute from anywhere.
Do you understand that ~/path/to/... is a dummy variable, to be substitute with the actual path to python3?