Two different vagrant environments can be run on the same machine. Here's how.
First, make sure you're initial vagrant environment is powered down. Move to the directory the environment is listed by running this command:
cd Desktop/vagrant
From there you can run the command to power it down.
vagrant halt
Second, when downloading the vagrant file and moving it to your Desktop in Step 2, call the folder something besides vagrant. For example vagrant-javascript.
Third, navigate to the vagrant-javascript folder instead of just the normal vagrant setup on your computer.
cd ../vagrant-javascript
Fourth, run the command to boot up the environment:
vagrant up
Fifth, continue on Step #5 of the process.