Typically, you'll want the orders that FarApp imports to post to NetSuite using a specific payment method. This payment method determines the account that NetSuite uses for the transaction since a payment method is associated with a particular account in NetSuite.
For most connectors the payment method your customer used for an order is known and so the most common setup is to have a corresponding payment method in NetSuite for each payment method in the marketplace/cart (e.g. Visa, MasterCard, PayPal, etc.). There are some marketplaces (e.g. Amazon) where the payment method isn't available and so the most common setup is to create a payment method in NetSuite for that marketplace (e.g. payment method "Amazon").
In a default NetSuite setup, you'll find your existing payment methods and can add new payment methods under Setup->Accounting->Accounting Lists (setting the filter at the top to "Payment Method"). Once you've added payment methods in NetSuite, they'll be available on your transactions. In a default NetSuite setup, on a sales order you'll find the payment method field under the Billing tab and on a cash sale you'll find the payment method field under the Payment tab.
Once you've created your payment methods in NetSuite, please follow the instructions in the "Mapping Payment Methods in the “Payment Settings” Page" sections here: