When I purchase inventory that I will be reselling, in what category do I put the expenses?

Well QBSE does not do inventory.  inventory when purchased is an asset until you sell it, then the cost of what was sold becomes an expense (COGS)

QBSE does not allow for any new accounts (categories) to be created
QBSE does not have sales receipts, only invoices
QBSE does not allow for journal entries
QBSE does not have the class function
QBSE does not do recurring transactions
QBSE does not keep a customer or job listing
QBSE does not have a balance sheet so you can not enter the cost or the depreciation for a car/equipment
QBSE does not do inventory or cost of goods sold
QBSE can not do payroll
QBSE does not do any associated IRS forms, like home office deductions or depreciation
QBSE will not accept a banking file formatted as .qbo (a standard intuit type of file)

QBSE does not do sales tax either (not schedule C related but critical to a business)

If you're doing under $1 million in sales, you don't need to track inventory or cost of goods. (Consult your tax professional.) In this case, treat it like any other receipt. I generally use "Other business expense". If you're doing anything to the items first (breaking them apart, combining parts, etc.) then use Materials and Supplies instead.

Once you hit the million mark, upgrade to a higher level of QB and use Cost Of Goods Sold.

The free TurboTax subscription that comes with QBSE handles the IRS filings, depreciation, etc.