To activate a Geneious personal license you need the FLEXnet licensing software. Normally this is installed automatically as part of the Geneious installation process, but in some cases you may need to run Help->Install FLEXnet from within Geneious before your license can be activated. Geneious will prompt you if this is the case.
Installing FLEXnet requires administrator privileges. However, the admin should not activate the license in their account if Geneious is to be run in another user's account, because personal licenses are only available to one user on a machine. If the license is activated in the admin's account the actual non-admin user will not be able to use the license. If you must verify that the license works, make sure you release it using the Help menu item. Note there is a limitation on the number of times a license can be released to prevent license sharing.
FLEXnet licensing only needs to be installed once by the administrator after which, the user can upgrade Geneious as a non-admin.