We recommend logging in before registering for your booths as this will assign the booths to your profile. This will make it easier to edit your booths and check the payment status as well.
To begin registration click a green pin on the map then the registration button in the box that appears.
You can also register for multiple booths at the same time. Once you click the register button on one of the booths you want it will let you add any additional booth numbers for registration.