You'll need an AWS account and some idea of which instance types you wish to reserve and for how long. Refer to the reserved instance properties that were mentioned previously for the exact information you'll need to proceed.

The Payment Option you choose will dramatically affect the price you pay when purchasing the reservation:

• No Upfront: This means you pay nothing now, but you will be charged the discounted hourly rate for the entire term, whether or not you have an instance that matches the reservation. Also, note that choosing this option limits you to one year for Standard reservations and three years for Convertible reservations.
• Partial Upfront: These reservations mean that you pay a smaller upfront fee, and then you are charged a discounted hourly rate only for the instance hours you use.
• All Upfront: As the name suggests, you'll be required to pay the full cost of the instance for the entire term. An effective 100% discount is applied to the hourly rate of your matching instances for that term.

Once you know all the properties of the instance reservation, you can go ahead and make a purchase.