hello,
i see admin must activate link manual for download product before email is sent to customer. how do i activate download and send email automatic if payment success?

Hello,
 
The downlodable links can be approved automatically when order was paid or later manually by administrator.
In order to make this process automatic be sure that your order status for success payment has 'Activate' option selected for 'Download Activation' field.
To send links with order confirmation message you can use special {links} tag.
 
Thanks,
ViArt Support Team