Files

New drawing

new_drawing2

Save

save
⌘S
Menu > File > Save

Open

open
⌘O
Menu > File > Open

Import photo

import_photos
⌘I
Menu > File > Import photo

Export as png

To export the drawing as a flattened .png
export_png
⌘E
Menu File > Export as png

Export layers

To export the drawing as a folder of layers
export_layers
⌘O
Menu > File > Open

Export with transparent background

1 - Draw on a layer above the paper layer (you can merge all layers into one to get your complete design)
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2 - Choose "export layers” in export options.
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3 - In your export folder, you will find your drawing layer on a transparent background, separated from the background paper layer. 
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Print

Press Cmd + P or click in the menu on File then Print
print
⌘P
Menu > File > Print