1. Open the bank feed. Go to Transactions (or Banking), choose the account, and look at the For Review tab, where every imported line sits until you decide what to do with it.
2. Let QuickBooks show you what it found. When QuickBooks recognizes a line as corresponding to something already in your books, usually because you created an invoice, entered a bill payment, or wrote a check for that amount, it labels the row Match and shows you which existing transaction it thinks this is.
3. Confirm the match is actually correct. Check the date, amount, and payee against what QuickBooks found. If it's right, click Match. Nothing new gets created; QuickBooks just links the bank line to the transaction you already entered and moves it to the Categorized tab.
4. If nothing matches, categorize it instead. When QuickBooks has nothing on file to connect the line to, it shows Categorize, the newer label for what used to just say Add. Pick the category and payee and confirm; this creates a brand-new transaction in your books, since there wasn't one there yet.
5. Watch for a wrong match before confirming it. QuickBooks suggests matches based on amount and rough timing, which occasionally pairs the wrong two transactions together, two invoices for the same amount paid around the same time, for instance. Confirming a bad match links the wrong records together, so it's worth a second look whenever more than one transaction could plausibly fit.