Hi, if I read correctly for an animation layer -

1) create blank keyframe on frame 1 then draw or paint on layer.
2) turn auto frame on?
3) click with stylus or mouse or use arrow key to jump to next frame
4) click add frame to add empty frame
5) turn on onion skin lightbulb to see previous frame underneath
6) draw new frame
7) return to step 3) onwards and cycle for new frames.

OR

1) create blank keyframe on frame 1 then draw or paint on layer.
2) click with stylus or mouse or use arrow key to jump to next frame
3) click add frame to add empty frame
4) turn on onion skin lightbulb to see previous frame underneath
5) draw new frame
6) return to step 2) onwards and cycle for new frames.

As it is - I don't see how pressing auto frame actually does anything? I've tried this on a PC and a Mac and auto frame does exactly the same thing (nothing)

Help? (New user here)

With Auto Frame Mode enabled, you can directly continue from the contents of the previous frame in your timeline without having to duplicate and move it by hand.
Try it - activate Auto frame, draw a brush stroke on the first frame, pick the second frame and draw another stroke on it, pick the third frame and draw another stroke, and so on. Now when you scroll through the frames or press play, you can see the progression.