Connect your Flora to your computer with a mini USB cable. Be sure your battery is either unplugged or that the Flora's onboard power switch is set to off.
To download the Flora TV-B-Gone software from Github, click the "zip" button highlighted above in purple.
Extract the zip file and rename the resulting folder "Flora_TV_B_Gone"
Move the folder into your Arduino sketches folder, which is located in your Documents folder by default on OS X. This is where your Arduino software looks for programs to edit and upload.