Hi Nick,
I think you will find that the 21 day trial only applies to those with SBS or Radarbox etc.
If you are download only, you will need to register and pay for Planeplotter first.
If you need any help, just look at the Planeplotter forum, it may seem complicated at first, but it's worth sticking with it,
It's a great piece of kit for the money.
Gaz....