You used the Easy One-Click. The Advanced One-Click lets you upload plugins.
In the same section you used to create the Easy One-Click, there should be a listing of it along with the option to delete it. Once it’s deleted, you’ll need to go to Manage Domains and Add a new domain as Fully Hosted. Once that’s done, go back to One-Clicks and used the Advanced Section to install WordPress into your Fully Hosted Domain.