I ran the thread through the 6th peg and locked it down with the locking mechanism. That's a post inside the peg that's tightened with the big flat wheel at the bottom of the tuning machine.
There is a post inside the tuner post that rises when you tighten the nurled wheel, which pins the string going through it against the inside top of the post. That keeps them from slipping and losing tune.
So anyway.... Through the 6th peg, into the 6th hole in the bridge, under and back out the first hole and up to the first peg.
Now I've simulated where the strings will be. I can line it up laterally by eye, compensating for the thicker bottom (closer to the top as you hold the guitar) strings.
I want the strings running as parallel as possible and centered. The dark line running up the guitar is center as it happens. That's from gluing 2 pieces for the body, and being careful to center every thing I do to the top and the neck.
Not just eyeball here, I checked to confirm
The 12th fret is the middle of the string length, so if my distance from center line is the same there and at the first fret and the 22nd, it's straight.
And it is straight. If my neck pocket wasn't square, or if my neck wasn't attached properly, I'd have work to do fixing that. But I was extra careful, so this worked out well.
Now, I mark the hole location by tracing the bridge and finding the center of the post.
The posts are 2 1/4" apart at center
I stopped there because it was getting late and I wanted time for things I forgot to bubble up to the surface of my brain.