First of all.......when the NT speaks about "flesh", it not talking about your body.
Its referring to being carnally minded......and that means, that the mind is not renewed, which means its "in the flesh".
So, when Paul says........."you are in the flesh"........He means......you are in a carnal mind, and that mind cannot understand or receive anything from the spirit of God. (bible).
So, a carnally minded person, looks at the bible like its a dictionary. They read it, trying to use human thinking (analysis and logic).. to understand it, and that can't succeed.
So, how does one get into the "spirit".
A.) Jesus said......""YOU, (everyone) must be born again"... = Spiritually, as that is how you "get in" the spirit.
However this does not deal with the human thought process, that remains carnal... so, what you have to do, is fill your mind with the "spiritual", and that means....... bible study and meditative prayer........so that God can give you "inner" revelation.. .as that is how a CHRISTian, learns the bible. along with finding an excellent NT teacher who can show you so much, and grow you quickly "in the spirit".