Select the Chest Lid as the Entity Reference

When you make an EntityRef on a script, dot big bang does some magic that will let you pick which entity you want to reference from the Entity menu, from a list of all the entities in your world right now. 

1. With Chest-Lid selected, open the Entity menu, and go to the Script section.
2. Scroll down until you see Chest Lid Ref, which corresponds to the chestLidRef variable you made in the last step.
3. Click the ⋯ icon to open the Select an Entity menu.
4. Select Chest-Top and click the Select button.