If you bought premium hosting, the first thing you should do is contact iFastNet. They provide the premium hosting, they provide the support for premium hosting, and they can migrate your website from our free hosting to their premium hosting, which is what needs to happen if you actually want to use the premium hosting.
InfinityFree doesn’t provide premium hosting, we can’t provide support for any premium hosting, and paying money to iFastNet doesn’t change anything about the service you get from us.