Assign an imported image to an image slot
In 
Images, click an image slot to open its settings.⚓
Use the arrows to browse through the image slots.
In Identification > Label, enter a label to rename the Image slot.
In Option, enable Allow downscale to resize the image when the image slot capacity is too low for the image resolution.
In Display, select an image from the Library to be used in this image slot.
The selected image is now loaded to an image slot and is ready to be displayed in layers.