The plastic you see covering the directional arrows are called knockouts. Simply pop out the directional arrows, as appropriate for your light fixture location.Remove the faceplate/cover then pop the plastic piece(s) out to reveal the backlit red arrow, when appropriate.Leave the directional arrow knockouts in place when you do not need a lit arrow. Remove them when you require an arrow to help point the way to safety. Base this decision on where you mount the light fixture so the arrows can point the way to a safety exit to the left or right of the sign.