How to get orb in astd?

Hey there, I'm a bit confused about something. I've been playing ASTD for a while now and I've heard about these orbs that everyone seems to be after. Can you give me a step-by-step guide on how to get orb in ASTD? I've tried looking online but there seems to be a lot of conflicting information. I'm hoping you can clear things up for me and maybe give me some tips on how to optimize my chances of getting them. Thanks in advance!