My Flex radio found it all by itself. Just install the latest version of SmartSDR. If your radio is not licensed for this latest version, it will take you by the hand and guide you to purchasing the license. Just follow the bouncing ball.
If needed (new radios or certified pre-owned radios purchased since May 19, 2017, do not need a licensed purchased), you purchase the license from the SmartSDR client. Just refer to the SmartSDR for Windows v2.2.8 Release Notes.