I assume you have created the logiblock and all the required applets from IFTTT to apilion.
you need to send a trigger back to IFTTT
At the bottom of the logicblock you will have this
In action chains positive result you need to put something like rainmachineon
in actions negative results rainmachineoff
go to IFTTT
Apilio applet select the only one there and you will get a drop down menu select rainmachine on. Then go to your rain machine applet and select on
Then repeat for off