Where should beginners learn SLR photography?

Practice is the most important thing. Read the instructions first, then practice. Learn photography theory and read introductory books, such as Simple Introduction to Digital SLR Photography. I summed up the steps myself, and every step below is to practice first, and then practice the next step.

Step 1: Take a picture with all the scenes clear.

Step 2: Take clear photos of the subject and other blurred photos.

Step 3: shoot with a high-speed shutter.

Step 4: shoot with a low-speed shutter.

Step 5: Shoot objects moving at low speed.

Step 6: Shoot high-speed moving objects.

Step 7: Shoot at night.

Step 8: Take a low-key photo.

Step 9: Take high-profile photos.

Step 10: Follow the shooting.

Step 11: pose and use natural light.

Step 12: pose and light yourself up.

Step 13: Take a snapshot and show the big scene.

Step 14: Take a snapshot and show the characters' expressions.

Step 15: Try to take a picture of yourself without a camera in it.

Step 16: Learn PS post-production.

Step 17: Innovate by yourself.

Step 18: Shoot with a flash.

You will find it more and more difficult, but if you pass, your photography level will improve quickly.

I wish you progress!