QB is designed to use perpetual inventory, that means you stock the item with cost and qty, and then you sell it. When you sell it, the cost is automatically posted to an expense account called COGS, Cost Of Goods Sold.
So first you create an inventory item named for the item you purchase (assumes you have the versions that include inventory), create the item with zero cost and zero qty.
Then you purchase the item, either a bill or just a purchase. When you enter the purchase you use the item details part of the purchase screen. Enter the item, the qty you bought and the total cost. Total cost includes everything, shipping, sales tax paid, brokerage fees, etc etc. There is a form at the sales tax site for your state that is called a resellers permit, you download it, fill it out, and give it to the vendor; that allows him to sell to you without sales tax.
To sell the inventory item you use it on a sales receipt or an invoice, enter the qty sold, and the total price it sold for. That will remove the qty from inventory and post the cost to COGS. The sales price will post to an income account
Inventory item screens have three required accounts:
asset = inventory asset
cost = COGS
income =- your income account for sales
