How do I 'Twin' my English village with one one in France?

I am thinking of proposing 'twinning' my English medieval village with the same in France. Neither are 'twinned' to anybody at present. How do I go about this please? Are there legal formalities etc? Is there an organisation that can help? What are the benefits of 'twinning'? It seems to be quite a popular notion. Most grateful for any advice. Thank you.