The virtual roles GoogleAnalyticsReaders and GoogleAnalyticsAdministrators to authorize editors to the gadget and administrators to the administrative interface. Please add this in <virtualRoles> section of <episerver.framework> config:
<add name="GoogleAnalyticsReaders" type="EPiServer.Security.MappedRole, EPiServer.Framework" roles="WebAdmins, Administrators, <your active directory group>" mode="Any" />
<add name="GoogleAnalyticsAdministrators" type="EPiServer.Security.MappedRole, EPiServer.Framework" roles="WebAdmins,Administrators,<your active directory group>" mode="Any" />
