LTM pool member enabling issue

Could you please help with my scenario as I basically have three pool members 2 are green and currently handling traffic and enabled my other previously added one and it is inactive and 0 traffic is through it, how can I have this activated do I have to reapply with updating all the pool members after enabling process or proceed with failover testing to direct the traffic to the other inactive pool members or update the pool or any other activity? device is already in sync with standby one.