What do you do for work?

My understanding is that you have to show that you have experience that matches that level. I'm a late-career government employee (just turned 40 with only 1 year as a fed at the FAA) and I just had to show comparable experience (mine was as a contractor) at the appropriate level. My situation was unique in that I had almost 20 years experience on my resume when I applied and got picked up as a fed.

You can look at the Office of Personnel Management (OPM) site for detailed descriptions of the positions and what the responsibilities/expectations are.