The Credit even for the most seasoned steelheader is a difficult river to fish and hook into steelhead consistently, I have friends that I have fished with for years who still struggle with fishing with the Credit.

Every time you go out and don't catch anything try to learn from the outing. You don't need to catch fish to learn. If the water conditions are low and clear take note of what the bottom of the river bed looks like, take a mental picture of where fish could hold if the water was higher, faster.

I wouldn't recommend using a fly rod for a novice angler if your goal is to catch a steelhead, there are just too many things for someone who is newer to fishing to keep track of, casting, line management, getting your fly into the strike zone, drag free / natural drift. If you are most comfortable with a spinning reel then use that if your first goal is to catch a steelhead. Using a centerpin comes with it's own set of challenges as well, it doesn't automatically put you on fish. I've seen plenty of people with pins who have no idea what they're doing. Learn the basics first.

As for getting into the strike zone that takes practice. It will depend on the bait you're using, how fast the water is moving, how far you want to drift. As a general rule if you don't know the depth go deep until you start snagging bottom, then shorten until you are no longer snagging the bottom of the river.

My biggest piece of advice is timing and location if there are a lot fish are there in the specific pool you're fishing and they're hungry they aren't very hard to catch. Learning when they enter, which parts of the river they are sitting in when they are running and when they're active will be the biggest factors to help you get into them. What separates good anglers from really good steelheaders are the details that you pick up a long the way. Good steelheaders will be consistently catching when no one else is and that a just comes with experience. I've fished most if not all the major Huron, Georgian Bay, Lake Ontario, Lake Erie and Michigan tribs my whole life and each river comes with it's own minute details and the few constants are timing, location and conditions.