You can display a reference window to import an image and place it anywhere in the canvas.
Open the menu in the top bar and tap on the reference 
icon to open a reference window. Tap on it a second time to hide the window.
Tap on the import icon to choose your image from the Photo Album, your Files, or directly shoot a photo with your iPhone.
Rotates the image 90° clockwise.
Fits the image to the size of the window.
Deletes the reference window.
Drag the corner arrow to resize the reference window.
Use 2 fingers to pinch and zoom in and out directly in the image.
