How do I fill an element with Age calculated from DOB date?

[Sunmaster]

I have spent days trying to figure out how to do this. I have searched the forums and google, but still don't know what to do. Please give step by step instructions. I saw some threads that had the same problem, but don't show the solution using Fabrik. Where do I put the code? Which code should I use? Should I use a plugin? If so how?

Thank you!