With the seller's/vendor's consent, you can bypass the sales page and send people straight to the Checkout page.
BUT only with the seller's/vendor's consent!
The format is this:
affusername = affiliate username
sellerusername = seller username
sku = product sku (found inside your product settings >> general settings >> top left)
pricenumber = if the product has multiple prices, replace this value with the price number (1 - 5). if there is only a single price, replace this value with "1"