Install latest Arduino IDE from arduino.cc

Open Terminal and execute the following command (copy->paste and hit enter):

mkdir -p ~/Documents/Arduino/hardware/espressif && \
cd ~/Documents/Arduino/hardware/espressif && \
git clone https://github.com/espressif/arduino-esp32.git esp32 --depth 1 && \
cd esp32 && \
git submodule update --init --recursive --depth 1 && \
cd tools && \
python get.py 

Where ~/Documents/Arduino represents your sketch book location as per "Arduino" > "Preferences" > "Sketchbook location" (in the IDE once started). Adjust the command above accordingly if necessary!  

If you get the error below. Install the command line dev tools with xcode-select --install and try the command above again:

xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

xcode-select --install

Try python3 instead of python if you get the error: IOError: [Errno socket error] [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:590) when running python get.py

If you get the following error when running python get.py urllib.error.URLError: <urlopen error SSL: CERTIFICATE_VERIFY_FAILED, go to Macintosh HD > Applications > Python3.6 folder (or any other python version), and run the following scripts: Install Certificates.command and Update Shell Profile.command

Restart Arduino IDE