Welcome to the forums my friend. You have the same transmitter I have and you want to set up flaps. It's pretty easy actually, except I use the laptop and not the phone app, should be similar though.
You plug the y connector from the flaps into channel 5 of the receiver, then on the app you go into channel set up. Scroll down to channel 5 graph and underneath it should give you a drop down window to select a switch, if disengaged it should say "inhibit". Tap on it to get the drop screen which will give you a list of switches to select, choose "flaps switch". This will give you the flaps control on your transmitter and give you 3 settings for flaps, closed, half and full. Hope this helps