How do we adjust our tv
You didn't mention anything about a cable box, VCR, etc. which might be connected. A snowy pic. means simply, inadequate signal is reaching the tuner, or the TV tuner itself is bad. If the first is so... check your cabling. If you have a VCR or DVD player hooked in between the cable box or outside antenna (whichever is the case), VCR (RF or ant.) out should go to the TV, VCR antenna (RF or ant.) input to the cable box.
Also check the cable wire itself. If you look at the end of the cable, you should see a relatively thin center wire. This center conductor is what carries the signal. If it is missing, bent over, or too short to make contact with whatever it is connected to, you will have a very snowy pic.
If you have a spare TV, connect it in place of your "new" TV, to narrow down the problem.
Lastly, if all is well with hookup, cabling, etc. the TV might have a problem. Sometimes the tuner has a component defect, or the coaxial connector can be broken.