Not easy to help on a theoretical basis at a distance...
The first step, is to loosen the parts of the chain that are folded back onto itself. If the tangling was violent that may require the use of strength and pliers...
Then it becomes easier to see if there are loops that need to move over something else.
As mentioned above there should be a quick link on the chain, opening that will help with the final step of entangling as you dont need to figure the loops, you can just move the open end of the chain as needed through the loops