You cannot send an e-mail
When you have decided where you would like to eat call (from the UK)
001 407 939 9463 (001 407 WDW DINE)
You will be given some options, you know, if you want this in English press 1 etc....
When you get through the cast member will ask how they can help you, just tell them what you want, for the first booking they will take a few details, such as booking number if you are stayng at disney, or telephone number, and then the rest will be linked to the same detials. I suggest you use your telephone number.
For each booking they will give you a reservation number, it is useful to keep these when you go to the resturants, just in case. If you do loose any of these they will be able to retrieve them using the telephione number you gave them (or booking ref number).