You don't want to change size of Sprite, and does it mean that you want to display Sprite of the big size?
SPDEF 0,U,V,W,H,0,0,1
U,V=Coordinates of the original image to define
W,H=Size of the original image to define
SPSET 0,0
SPOFS 0,X,Y
X,Y=Screen coordinates where the sprite will be displayed