adjusting pressure on new regulator

I see in one of the posts on this topic there is a vacuum gun attached to the regulator and then a torx bit. How is this actually done? Is the vacuum guage pump to 17 lbs or do you leave it at zero and then turn the torx screw till the gauge reads 17? I don't own a vacuum pump/guage and will be buying one when my new MFI uprgade shows up soon. Thanks for any info.