Meteor doesn't exist in isolation, and it's common to install a number of extra tools for development, such as Mongo, Robomongo, Atom, Linters, etc.
# make sure mongo is in your local path
nano ~/.profile
export PATH=$PATH:/usr/local/mongodb/bin
# or install it to the global path
nano /etc/paths
/usr/local/mongodb/bin
# create mongo database directory
mkdir /data/
mkdir /data/db
chown -R username:admin /data
# run mongodb server
mongod
ctrl-c
# check that you can connect to your meteor app with stand-alone mongo
terminal-a$ meteor create helloworld
terminal-a$ cd helloworld
terminal-a$ meteor
terminal-b$ mongo -port 3001
# install robomongo database admin tool
http://robomongo.org/
# check you can connect to your mongo instance with robomongo
terminal-a$ meteor create helloworld
terminal-a$ cd helloworld
terminal-a$ meteor
Dock$ Robomongo > Create > localhost:3001