1. Start up Terminal
2. Type cd ~/ to go to your home folder
3. Type nano .bash_profile to create your new file.

alias dir=pwd
alias startDocker="docker-compose"
alias chrome="open -a 'Google Chrome'"

4. Type source .bash_profile to load the file in your terminal.

Via https://stackoverflow.com/questions/8967843/how-do-i-create-a-bash-alias