You would normally torque it up with a torque wrench.
Then with a smaller torque wrench measure the preload.
Use this type of torque wrench

Or

What most of us do is carefully remove the nut, pull out companion flange remove / replace seal and install companion flange again with a little sealant under the washer.
Then install the nut in exactly the same place as it was before.
Only need to use the preload settings if you have installed a new crush sleeve.
There are heaps of tutorials on google....
Calvin