This might help: the feeler gauge goes between the valve stem and the rocker tip.....and if you have to ask that particular part of the question...I would suggest you get some help your 1st time doing this.
with #1 piston TDC on compression stroke (#6 rocking) you can set:
Intakes 1-2-4
exhaust 1-3-5
set intakes to .010" (or the cam's recommended lash)
set exhaust to .020" (or the cam's recommended lash)
find #6 TDC compression. mark crank damper and gear cover turn engine over 1 rev. you verify this when you see #1 valves go into overlap (rocking).
now you can set rest....
intake 3-5-6
exhaust 2-4-6
How To Set Valve Lash On A Diesel Engine - YouTube