Save the docker-exec-shortcut.sh file to your local environment
Then modify the CHMOD of the file so that it is executable:
chmod +x docker-exec-shortcut.sh
Copy the file over to the /usr/bin directoy:
cp docker-exec-shortcut.sh /usr/bin/
Now you're all set to use the shortcut from anywhere on your machine:
docker-exec-shortcut.sh CONTAINER_NAME