Download and install Arduino IDE from here: https://www.arduino.cc/en/Main/Software
Once Arduino IDE is installed, the red lemur core needs to be installed in Arduino IDE.
Add the address to the additional boards manager: https://s3-us-west-2.amazonaws.com/redlemur.io/package_red_lemur_index.json
Scroll to the bottom of the list and click on the Red Lemur entry to see the install button. Click the install button to install the Red Lemur core. This process can take a couple minutes to complete. When it is complete, click close.
Congratulations! The Red Lemur core is installed in Arduino IDE and you are ready to make something amazing.