Hey Randy,
First you'll need the sump tank itself, an overflow to pull water from the tank in a constant siphon, and a pump in the sump to return the water back up to the tank.
The sump should be at least 1/4 to 2/3 the size of your tank to be safe. Optimal sump setups for biological filtration call for sumps that are 1/2 again as large as your main display.
There are several posts throughout this forum that discuss this subject and have many of the answers you are looking for. Try doing a search for Sumps or Refugiums to pull up a list of the threads that discuss this.
Come back with any questions you still have after reading through the available material and I'll take your questions from there. Of course I hope others will still contribute their suggestions in the meantime.
HTH,
Aaron