The Package owns a set of ProfileApplications (not shown: the Association subsets owner/ownedElement). Those allow to navigate to the Profiles.
It is possible to dynamically apply profiles and the process is detailed in the specs. For example when applying a profile all required Stereotypes must be created for the extended metaclasses. Also removing a profile will destroy all stereotypes that are part of the profile.
A more important feature of profiles is that profiles are exchangable as xmi data. So profile created with one tool should be readable by another tool.