As @ZebraBlinds mentioned, The first generation Lowe’s Iris zigbee devices cannot be made to work with SmartThings. You will find much discussion in the forums about them.
The second generation, which uses the zigbee home automation profile (ZHA 1.2) will work. So will most of the Z wave devices.
Zigbee standard allows for many different profiles and they can be very different. They don’t even all use the same addressing scheme. SmartThings uses the zigbee home automation profile.
So the best thing would be to return the first generation one that you bought and instead buy the second generation: