An apple is an excellent subject for a painting whether you're a beginner or more experienced painter. The famous modern artist Cézanne painted many an apple. As a beginner, it gives you good practice in painting a realistic subject that's a step on from painting a sphere. For an experienced artist the challenge lies in the composition, deciding how to position it and arranging the light to produce an interesting result.
When setting up a still life for a painting, you want to position the subject (in this case the apple) and your easel so you can see both without turning your head much. The photo shows how I'd set things up for my painting. I was standing in front of the easel and set the apple on top of a table, painting with the brush in my left hand.
To lift the apple higher, so I wasn't looking down on it quite so much, I propped it up on a box. The apple is sitting on colored paper I'd selected as my foreground and background colors.
The key to painting a realistic apple is knowing how to use tone so it looks three-dimensional, rather than like a flat circle. Go from circle to sphere to apple...