If you're referring to the set object collision to polygons command I mentioned, here's a simple example for you to take a look at.
make object sphere 1, 1
set object collision on 1
set object radius 1, 2
make object plain 2, 50, 50 : xrotate object 2, 90 : position object 2, 0, -50, 0
set object collision on 2
set object collision to polygons 2
do
if object collision (1, 2)=1
if upkey() then move object 1, .05
if downkey() then move object 1, -.05
if leftkey() then yrotate object 1, rot# : rot#=rot#-.1
if rightkey() then yrotate object 1, rot# : rot#=rot#+.1
else
move object down 1, .01
endif
set camera to follow object position x(1), object position y(1), object position z(1), object angle y(1), 30, 5, 50, 0
text 1, 1, "Use the arrow keys to move the ball"
LOOP