using public Transform target

How do I define the target? Using transform.LookAt(target) but I don’t know where to set the target also, I have several targets to look at, should I use serializedObject? if so, where do I set the list of serialized Objects?

public transform target; /Public makes the variable appear in the unity editor window itself so it is just a simple drag and drop procedure from there.Then go where you have attached the script to a gameobject and drag the target into the slot titled target/

Also if you have more than one target you could just make extra variables: target1, target2, and on or you could make a list/array of transform objects. Look at tutorials in Unity documentation if you want to do that