I am designing the rebate/coupon site i have done all the coding and shows the coupong but now the problem arises for me. its my first work on rebates i dont know any thing about tracking the order and sending to the merchant site.

how i send the user to merchant site and track the purchase so i can calculate the commission the site owner gets from the merchant site.
i have learnt that the affiliate or pixel tracking is used for tracking the transaction but i dont understand how to use it.

Please help me this is the last thing i have to complete the site.