you just need to place the objects on a empty map, save it then open the mission.sqm in a text editor and you see something like this
class Item0
{
position[]={9883.478516,26.730000,4080.480957};
id=1;
side="EMPTY";
vehicle="MASH";
leader=1;
skill=0.600000;
vehicle="MASH"; is the name of the object,just to get you started "mash" is a feild hospital and "fencewood" is a sandbag wall.