At the moment, we don't yet have a feature built into the UI to handle adding your shipping account.
If you are in the US and would like your order shipped via your company's UPS or FedEx account, please create an issue once your order is placed requesting this. Shipping on FedEx accounts will result in a one day delay in shipment due to scheduling a pickup for next day.
If paying via credit card, we would then deduct the shipping charges from the quote.
If paying via wire transfer, please exclude the shipping charges from the amount you would wire.
For reference on the issue system, please see this article: