Please re-read instructions for installing a sink on this page. You can also find an article on double sink vanity on this website.
Anyway, your water supply lines should have T shaped fitting to feed the both faucets on the sinks. You will need to purchase a new waste pipe set up. You also need an outlet waste depending upon the position of your drain to the sinks.
The best way is to install all faucets and drains to the vanity sinks before you place the vanity in place.
