Hi,
as soon as you order your theme, and payment is processed, you can download the theme you purchased and start using it on your WordPress installation.
iThemes can provide additional services, check out http://ithemes.com/services/ or contact one of the WordPress developers if you require additional support: http://ithemes.com/services/wordpress-developers-list/
These additional services are not included in the purchase of your theme though.
Hope this clarifies,Ronald

