How to connect Intel Edison to Arduino

G’Day guys, just a quick question, how do I connect an Intel Edison that as a Grove Base Shield (see pictures) which has a UART port on it to an Arduino UNO that has a motor shield on it. How would I go about this code wise and wiring wise?
FYI I am building this: https://www.instructables.com/id/Indoor-CNC-Garden/ (Step 17 is talking about the Intel Edison setup)