Or
XSCREEN 4
and then move the sprites to lower than 239 pixels, although the [DISPLAY] is probably more useful
Be careful though because you cant use a sprite unless you called it from what the current display screen is.
So even if you say
DISPLAY 0
SPEST 0,0
... then typing in
DISPLAY 1
SPOFS 0,X,Y
will cause an error, because a sprite with management number 0 was not created on the bottom.
What kind of problem(s) are you running into?
Also, here is some basic code to show two sprites, one on the top screen, and another on the bottom.
Keep in mind, that the arguments for XSCREEN may differ due to the requirements of the program.