Just press and hold the button and begin scanning. You can press the button before, or after, placing it on the wall. Once the unit is on the wall, the lights will indicate the position of hidden objects in the wall. Franklin Sensors stud finders are unique in their ability to instantly find studs. (Other stud finders have a specific set of steps that must be followed for them to operate correctly). Note: This is not the case with our 3-sensor models.