Disclaimer: I haven't personally made this connection myself, but this is what the procedure should be based on similar experiences and a lot of time spent in both terminals.

As stated above, JetBlue is in Terminal C and El Al is in Terminal E. The 2 terminals are connected post-security, and there is nothing more than a line on the floor showing where you cross from one terminal to the other (between gates C8 and E1).

The transfer is essentially the same as a domestic-to-domestic transfer within one terminal: you get off one plane, walk to your connecting gate, and get on the second plane. No security checks, no shuttle buses, etc.