How do you attach a guitar strap?
Use a lace (sold separately) by looping it through the pinhole of one end of the strap and tying it around the headstock of the guitar by the nut under the strings. Put the pinhole of the other end of the strap over the strap pin of the guitar. Classical acoustic guitars are not equipped with any strap pins.
Which end of guitar strap goes where?
The end that's sewn directly to the nylon is the "bottom". As a strap it doesn't matter, but it makes it easier to adjust, and usually that plastic in the middle of the strap hangs to your side instead of digging into your back.