"Change Canvas Size" command in Canvas tool lets you change the size of the canvas.
Open ①the Tool Selection windowand select ②Canvas tool.
Select ①Change Canvas Size.
①Keep Aspect Ratio, which will keep the given ratio between the width and the height of the canvas. Turning off the aspect ratio will let you change the size of the canvas freely.
②Width(px) can be changed by pixel.
③Height(px)can be changed by pixel.
④Origin lets you align the canvas.
Tap on ⑤✓ to finish changing the canvas size.
Start drawing after changing the canvas size.