My cut off water pressure is 68psi trying to shorthen the window for pump to kick on its now at approx 42psi would like it around 55... tryed screwing out right screw or in doesn't seem to change... do I have to add air to the blater in the water tank? Thanks

Do not add air to the tank. First turn off power, then turn the large center nut clockwise until you get to the 55 cutin. This is not an exact science and you will have to do trial and error on it until your system cuts in at 55. IT will take several times of power off, turn nut, power on, check cut in point, and so forth. It will take several turns.

That will also increase the cut off pressure, so you will turn that down by using the small nut. Turn it counter clockwise until cutoff gets down to 68. BTW, 55 is rather high. It will increase the stress on your pump. In fact, 55 and 68 are pushing it a bit. Most people view a 40/60 setting as being about as high as you want to go. Whatever you do, be careful with the cutoff range. You don't want to get so high that the pump will not cut off.

You will also need to set your tank pressure to 2# below the cut in pressure, which for you will be 53#. Do this with power off and pressure drained to zero.

This site has a great description of this process. Look about halfway down the page.

How to adjust water pump pressure, pump cut-on pressure and pump cut-off pressure - private pump and well system do-it-yourself repairs