1. Open a new check. Click + New, then Check under the Vendors column.
2. Pick the bank account the check is drawn on. This matters more than it sounds like it should; picking the wrong account here means the transaction posts against the wrong balance entirely.
3. Pick the payee and enter the check number. If you're recording a check you already wrote by hand, enter the number it was actually written with so your register matches reality. If QuickBooks is going to print this one, you can leave the number blank and it assigns one automatically when it prints.
4. Assign a category (or several) to the line items. Same rule as any other transaction: split it across accounts if the check covers more than one kind of expense.
5. Decide whether to print it, then save. Uncheck Print later if the check already went out by hand or some other way and you're only recording it here. Leave it checked if you want this check added to QuickBooks' print queue, which is where the separate check-printing process picks up.