Choose in the menu Image – Image Size – e.g. under Pixel Dimensions (e.g. percentage-wise alteration) or Document Size (cm).
You can change the resolution of the image in the Resolution field. If a picture is small when you print it, even though it looks fine on the screen, it ́s possible because that the resolution is very high, in contrast to the pictures psychical size of the picture.
This applies to the following ”rule of thumb” for image resolution:
Images for screen use Images for use in print Images for printing on Images for printing on Images for use in print
in a newspaper
a laser printer
a inkjet printer
(offset-) printing company
Between 72 and 96 ppi (pixel per inch) Between 85 and 150 ppi
Between 180 and 225 ppi
300 ppi or more