Trace the wires carefully in the diagram so you can connect them to the proper locations. Keep in mind that the maximum allowable wires in a standard size electrical box is five 5. Take your time, mark the wires properly and you will not only be successful, you will stay sane. I think one of the reasons that people who are new to the platform get confused is just because SmartThings does have so many different options. In the main switch there are 4 Romex wire sets.
3 Way Switch Wiring Diagram
The wire that will be hot when the circuit is completed to your light usually black Traveler:
Help wiring a 3 way switch
In the other box it is: This option is helpful if you are adding a light to an existing building and it is easier to drop all the lines down from an attic instead of trying to get wiring up from a finished basement or trying to fish wire up two stories. I jumped the gone on that statement above. This is great.