As I can check here, you need to bring up the vagrant environment first and ssh into the vagrant instance by running the following commands in terminal from within the m103-vagrant-env directory:
vagrant up --provision
When you are connected to the vagrant environment, then create your configuration file in the /shared folder and use the following command to start the mongod process:
mongod -f /shared/
I hope it helps!!
Please let me know, if you have any questions.