Hi!
The configuration on the Live Chat will remain exactly the same as you have done it for a single Extension, with the only difference that you need to get the Click2Talk link of a Queue in 3CX, not a single Extension.
Note that Queue are available in the Pro and Ent editions only.
Once you have the Live Chat pointing to a Queue, you can create multiple Users/Extensions on your system, once for each user, then add them as members to the Queue.
This way, once a chat comes in, it will go to the Queue and all Agents will see it, and can "take" it for handling.