To link the movements of an object to another object in a scene you will need to create a transform link. A transform link will force one object to follow another.
To create a transform link select the slave object and within the developer tab, right click and choose Create > View/Tracking Nodes > Transform link.
In the properties of transform link you have created set the source to the master object and set the target to the slave object.
You can now move the empty assembly around in space to position the slave object wherever you want in relation to the master object while still maintaining the link of the master moving the slave.