I think the gif is self-explanatory for the most part.
I have the frame in the layer I want to fill into selected. But it won’t let me fill in the shape in the layer, only in the whole image. So I try to hide/lock the background layer but it won’t let me because it thinks I’m trying to fill it in the background layer which is hidden/locked.
Make sure the right frame is selected and the top layer is green, not gray. That should do it.
Oh, I thought I had the layer selected because I had a frame in the layer I was trying to fill in selected. And I think Wick is supposed to always have your selected frame in the selected layer so when you click on a frame it will select the layer your frame is in. But when I click on the lock/hide button for a layer it selects the layer, but the selected frame doesn’t change. I think this might be unintended behavior.