If you've already installed Android Studio --
Add the following lines to the end of ~/.bashrc or ~/.zshrc (if using Oh My ZSH):
export ANDROID_HOME=/Users/$USER/Library/Android/sdk
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools
Restart Terminal and you're good to go.
Add the following lines to the end of ~/.bashrc or ~/.zshrc (if using Oh My ZSH):
export ANDROID_HOME=/Users/$USER/Library/Android/sdk
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools
Restart Terminal and you're good to go.