The reseller discounts are automatically applied when you purchase your app subscription. The no-branding option is automatically activated and you will not be charged for that option.
As a reseller you save approximately €250/$330 per app.
You will receive an invoice by e-mail for your own record keeping. If you choose to pay for your app via monthly subscription, you will get a new invoice every 30 days.
For apps paid annually, you will get a new invoice after 1 year. If you stop paying, the app will be removed from the app stores and any apps that have been downloaded will stop working (unless you choose to renew your subscription).