Ok so what you do is add "AddPropImpulse(string& asName, float afX, float afY, float afZ, string& asCoordSystem);" into your script file, replacing the "string& asName" with the name of the entity in question, and replace the "float afX, float afY, and float afZ" with the amount of force (in numbers) you wish to have applied to the entity in that direction, and leave the "string& asCoordSystem" as "".
So, for instance, with one of my objects it looks like this: AddPropImpulse("crossboo_1", 0, 0, -2, "");
EDIT2: Oh, and make sure that the string is put under (without quotations):
Hope that helps!
EDIT: Oh and if you don't mind, give me an Internet if it helped!