You would need to purchase the "Installation service" if you want someone to install it for you. You will need to make sure you have arranged and set up web hosting, domain name etc.
It should be right there underneath your license where you just went to purchase the extras. It's an orange link which will look similar to the following (but it will mention "install service").
Just submit the installation request and someone will respond as soon as they are able to. If you don't have all of the information, you can provide as much as you have, and any other information in the notes section.