WordPress VIP hosting is limited to one application per plan. That means you can install either one single-site or one multi-site (with as many sub-sites as you need) in one application. If you have one multi-site with multiple child-sites, it can be migrated over to WordPress VIP under a single application. If you have more than one single-site or multi-site, you'll need to signup for more than one plan. Contact us and we'll help you select the best option based on your needs.