Install the module. Should you already use the maintenance module and have equipments with field 'Preventive Maintenance Frequency' defined, a new maintenance plan will be automatically created on these equipments with maintenance kind 'Install'. Moreover if a Request of type 'preventive' exists, whose stage isn't marked as 'Request done', and has a Request Date matching the equipment's 'Next Preventive Maintenance', the request will be updated with the 'Install' maintenance kind. Make sure you don't have multiple 'preventive' requests at a stage which isn't marked as 'Request done' and on the same 'Request date' as the equipment or the module installation will fail with a User Error.