ThinkCentral is the platform used with Go Math! (grades 1-5) and Journeys (grades 1-4). It is a web-based platform, so there is no "app". We have placed a shortcut to the web address on all student ipads.
The following link is a support page at the ThinkCentral website: http://downloads.hmlt.hmco.com/Help/Ed/Student/#t=Overview_Student.htm