HOw do I erase
At its most basic?
Tap the active tool icon in the upper left as shown at number 1 in the screenshot. Then tap the eraser icon at number 2.
Tap the "brush" option under the eraser tool to adjust opacity, size, etc.
Be sure the layer you want to erase is active. (It might also help to toggle the visibility of layers above the layer you want to erase should you have multiple layers.)
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