Indego bike rental stations are located across the city. You'll need a US-registered credit or debit card to rent the bikes for the walk-up rate. A better deal is to order an Indego key ahead of time.
The IndegoFlex ($10 per year) gives you a rate of $4 per hour. The Indego30 ($15 per month) is the best deal if you plan to use the bikes a lot, as the first hour of every trip is free, before the $4 per hour rate kicks in.