All real planes will pitch up when you add flaps and it’s perfectly normal behavior. I’ve flown a few Cessna’s (my preferred plane was a 1973 Piper Warrior) and the lighter the plane, the more it ill pitch up when adding flaps. You generally hold the yoke forward when descending to approach with your left hand and extend the flaps using your right hand. Adding flaps increases your lift and will pitch the nose you as a result. You’ll need to press forward on the yoke to compensate while the plane settles and the speed decreases. You may have to adjust the trim (nose down) a bit if your air speed decreases too much or add power to compensate.
I have found the sim to be very sensitive to trim and changes in flaps. A real plane is much less sensitive if trimmed properly for descent and approach. Never flown a real C208 so I’m not sure how it handles in real life.
Happy flying.