Every person, and every single sewing machine has a different method or setting for making button holes, therefore I couldn't begin to tell you how the settings on your machine work for you. I recommend following your machine manual, and doing some trial tests. If you don't have a machine that makes buttonholes, you could hand stitch them (warning: satisfying but time consuming) or, if you live in any large city most alteration tailors and even some dry cleaners will be apply your button holes for you. I generally outsource my buttonholes as my machine doesn't do buttonholes. Even so, the tailor who applies your button holes will expect you to mark them first. There are some general rules for marking buttonholes:
There are button hole markings on the pattern for you to follow on the Olya shirt. However you should always customise the size of your button holes to match your buttons. Generally speaking your button hole should be around 3mm up to 5mm bigger than your button depending on the thickness of the button. If it is a large or round button the button hole will need to be even bigger. I recommend to do some test runs first. That will ensure your button holes are working well (and are the right size for your buttons.
On a shirt the front buttons always run vertically in the same direction as the placket. Make sure the button holes are lined up in the CENTRE of the placket.
On the collar stand there is one button hole and that is always horizontal (opposite to the body). This button hole is placed in the middle of the stand depth wise, but the centre of the buttonhole DOES NOT line up with the centre of the body, note the diagram above. It is set back slightly. This is because its more important for the buttons to line up, than the buttonholes.. to line up. If the button was in the centre of a horizontal buttonhole there would be too much wiggle room either side of the button and the neckline would open up and close, this way the buttonhole is pulled against the button.
When marking the button placement, the centre of the button goes in the middle of the vertical buttonholes.
You should place the underneath layer where you intend it go, as if you were doing the shirt up, then you can simply poke through the cut buttonhole with a pencil or invisible marker to other side, leaving a mark where the button will go.
With the horizontal buttonhole on the collar stand, the centre of the button will be positioned not in the middle of the hole, but aligned with the buttons on the placket which are all at the centre front. So, the button will be positioned 5mm from the outside edge of the button hole.
The buttonhole on the cuff is horizontal, and placed in the middle of the cuff. The distance from the start of the button hole to the edge of the cuff is 7mm and the button will be placed 3mm in from the start of the button hole (just like the collar stand) This lines the closure up with the centre of the 2cm wide placket.
Now you just need to attach your buttons!
But which sides do the buttonholes go? Left or right?
Traditionally, a mans shirt wraps left over right, and a womens shirt right over left.
While I cant confirm its truth, the theory is that a gentleman's sword was always worn on the left side, so that it could be drawn with the right hand. If a jacket buttoned right over left, the handle of the sword would be likely to catch in the jacket opening when drawn, so any serious swordsman would demand a garment which buttoned left over right. As an indication of a masculine lifestyle, this tradition was then extended to other items of menswear.
The theory behind why womens shirt are fastened right over left is that 'LADIES' were once dressed by maids or servants; it is easier for a right-handed person to button another's clothing right-over-left. Men normally dressed themselves, and the opposite method is easier.
However what my college teacher taught me was, womens shirts fasten right over left, because a woman is always right. I'm not sure about that, but it's certainly easy to remember at least.
I don't tend to prescribe to any fixed notions of gender, patriarchy or class systems, so when choosing which side of my shirt gets buttonholes and which side gets the buttons, I generally choose the one with neater topstitching. Feel free to do your buttons up however the hell you want.