Quote: "where the use click"
Well, determining where a user is clicking in 3d space is interesting since the screen is only two dimensional. To find the coordinate you have to determine how far way the object should be. Once you've decided this you use something like-
if mouseclick()=1
pick screen mousex(),mousey(),(the distance away you think it should appear)
x#=get pick vector x()+camera position x()
y#=get pick vector y()+camera position y()
z#=get pick vector z()+camera position z()
make object [cube,sphere,plain] (you have to keep track of the object number),(size information)
position object (object number),x#,y#,z#
endif
This code does nothing by itself of course, and it is completely up to you to get the information which is in parenthesis. I just wanted to make you aware of how the pick screen command works since it is useful in what you are trying to make.