How do we adjust our tv

Question

We are trying to tune in a tv that worked perfectly at its last location. We have plugged it into the coaxial cable here and now we have a picture but it is snowy and jumping. How can we rectify this? Our "old" tv worked perfectly before the picture tube gave up.Would you please be able to assist with this problem?The instruction manual seems to have been mislaid for our "new" tv.HELP PLEASE!