I want to add email field on the registration page and check it if the two email that the user input matched or not.
I am using eshop theme by templatic.
Any help would be appreciated.
This plugin may be exactly what you're looking for:
Optionally, you may opt to create your own registration page in Wordpress from scratch. This guide will help you:
jQuery would be the "proper" way to do it, but I am not that ofay with it, but it is possible to do in php like so