Can anyone tell me how to layout the exact distance between the postholes
for a privacy fence with sections that are 6 feet tall and 8 feet wide?

This privacy fence has 3 rails that will fit into bored out holes on the
posts. If I set the posts in concrete, how do I install the pre-built
privacy fence sections into the posts???

Hope this does not seem too dumb...
All help greatly appreciated !
Matt