How to animate frame by frame with onion skin.

First click onion skin, second set the marker to two frames so that you can select the second frame. When you have the second frame selected, you will see a transparent element in my case its a stickfigure. Everytime you draw with a brush or other tool you can draw over the previous frame (The previous frame is now like a template for you to draw over). When done with the second frame just make a extra empty keyframe for the third keyframe by hitting F7 for Windows, for Mac its fn+F7 if you have a compact keyboard otherways its just F7.

Thanks for reading :)