Code:
ENTITY* e1;
function fn() {
	// assuming that "m1" is the ("WED-assigned") name of some ENTITY placed in WED 
	//...and ENTITY "m1" is present in the currently loaded level
	e1 = ent_for_name("m1");
	if (e1 != NULL) {
		e1.x += 5;
		e1.y -= 5;
	}
}


see manual entry for term "ent_for_name"