UPDATE: On Sept. 26, this story was updated with the news of support for more-affordable third-party chargers.
In order to take advantage of the rapid charging feature, you'll need to buy Apple's USB-C adapter or specific supported third-party chargers. You'll also need a USB-C to Lightning cable from Apple or a third party.
If you use the Lightning port and the Lightning cable that comes with the handsets, you'll get the pokey battery charging you've grown accustomed to with older iPhones.
Apple's USB-C power adapters range in price from $49 to $79, and include wattages of 29W, 61W, and 87W. Add that price to the $25 you'll pay for one of Apple's cables, and you could tack on as much as $104 to the price of owning your shiny new iPhone.
You don't need to spend $49 on a compatible charger, though, as an Apple support document notes that "A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD)" will also grant you the speedier charging capabilities. That means Anker's $25.99 USB Type-C with Power Delivery 30W wall charger will do the trick for almost half the price.
You may not need to spend $25 on a Lightning to USB-C cable either. While the Apple support doc specifies that its own USB-C to Lightning cables should be used to gain fast charging, you can find affordable third-party options (such as this $8.99 option from Metrans) on Amazon. Unfortunately, the pages for it, and other third party options, do not list approval by Apple's Made For iPhone program, so their quality is unknown.
Apple could have simply included a USB-C port in the iPhone instead of its Lightning port. But Apple has long clung to its own technologies, which remains true of the iPhone 8 and iPhone X.
Another option is to go the wireless charging route with Qi wireless chargers. Two wireless charging pads, one from Belkin and one from Mophie, will support fast wireless charging once Apple issues an update to the iPhone 8 and 8 Plus. The iPhone X will presumably support this features at launch since it's launching later, but we'll have to see.
Apple's iPhone 8 and 8 Plus are currently on sale, but if you're hoping to get an iPhone X, that handset goes on pre-order Oct. 27 and won't ship until Nov. 3.