Have a Panasonic Plasma TV model TH42PHD5UY.  Does not have speakers. 
Recommends Panasonic speakers TYSP42P5wk (6 Ohm, 8 Watts per speaker.)
What other speakers can I use.  Does speakers have to be 6 Ohm?  Do
they have to be 8 Watts?  I don't know anything about Ohm or Watts?

for clarification: are you looking to mount these speakers onto the
plasma tv (like the panasonic speakers would?) if not, then the
wattage and resistance do not matter and any home theater system would
work

If you are connecting the speakers to the "speaker outputs" of your
TV, you should select a speaker with 6 Ohm or higher "nominal
impedance". A lower impedance will overdrive / overheat the audio
amplifier in the TV and possibly cause damage or a thermal shutdown.
Since most home speakers are 8 ohm speakers, you should be able to
find many models including "in wall" speakers.