MC75 OS Question

excuse me if this is not the correct board to ask this question.

I signed up and purchased a developer unit a couple years ago (mc75 with 6.1)

 

I finally got around to writing my application and purchased 4 units for my client, the new units came with a newer version of the Os, it looked really different than my developer unit.  So my question, how do I update the Os on my developer unit so I can walk clients thru any field usage of the OS?

 

I googled, and it appears the OS is a firmware update, but I cannot find any info on firmware updates?