They both have an IFTTT channel/service, so you can just use that.
Most people would just set up a virtual switch for this. Once you have created the virtual switch, it will show up on your list of devices just like a physical switch.
You can then turn it on or off manually with smarttiles or turn it on and off in a routine or other automation.
So the SmartThings switch coming on is the “if” in your IFTTT applet and then skydrop turning on is the “that.”
Then create a second IFTTT applet where the SmartThings switch turning off is the “if” and skydrop turning off is the “that.”