I haven't done this in years, but the general procedure is the same -- I just don't know the specific specs off the top of my head....
It helps to have a buddy help you when doing this. Basically you want to measure the sag with your weight on the bike & the sag with no one on the bike. If I remember correctly, your supposed to shoot for 1.5 inches of sag with all your gear on -- but check on that because these new bikes could be completely different... and my memory has a high probability of being shot!
1st measure the distance from a point on the rear fender to a point on the ground -- & remember exactly which points you choose for consistent measurements. Then get on the bike & have your buddy measure that same distance & subtract the difference in the 2 measurements. You'll want that difference in measurement to be within a certain spec, depending on your riding style.
To decrease the number, turn the ring on top of the spring downward, to compress the spring. To increase the number, turn so the nut spins upward, extending the spring. If you don't own a spanner wrench, you can carefully use the hammer/screwdriver method if your not picky with looks. That method tends to put divots in the tangs if your rough, or the screwdriver is too sharp-edged.