A big welcome to our Forum. As the RWFF software is a fishing simulator (versus being a fishing game) the technique of catching a fish is very similar to what you would use in real life fishing. I don't have the Fishing Simulator on my iPhone yet but I have it on my Android Phone and the program is the same. To catch a Steelhead you would need to use some kind of streamer fly, cast the fly across the current and let it drift down stream with the current. Cast to likely fish holding places and try various depths. If you do this right you will be rewarded with a strike, and maybe even a good fish.
The Fishing Simulator is a smaller version of the Real World Fly Fishing desktop software. To get all the features and over 1500 different custom outings (all free), you can try the desktop version of RWFF and you will have lots of fun catching all varieties of fish in many exotic fishing destinations from around the world.
You can download the free demo at Pishtech and see if you liked it before you buy it too. A good deal.
Have fun and good luck!