A good free place to start is Cambridge in Colour. It’s widely recommended for clear explanations of core photography topics, and its forum is useful when you have specific questions.

For a more structured beginner path, books are often better than random online videos. Two commonly recommended beginner books are:

• Understanding Exposure by Bryan Peterson for exposure basics
• The Photographer’s Eye by Michael Freeman for composition

If you specifically want help with Nikon DSLR controls and menus, a Nikon D5200 tutorial was recommended on Kelby Training/B&H Camera Basics. Even though it’s for the newer D5200, much of it should still be helpful for understanding Nikon menus, metering, autofocus, flash, and video. It isn’t free, but it may be useful if you want a guided camera walkthrough.

In short: use Cambridge in Colour for free online learning, add a structured beginner book for fundamentals, and use a Nikon tutorial if you want help with the camera’s specific controls.