I want to share about this wig because it's one of the more challenging wigs.
As with any parting twintails, you should take caution not to tug on the twintails. If they come undone, it's hard to tie them up neatly again.
Store the twintails with a hairnet around the tails. Put the wig on first without removing the hair net. Then release the tails gently by pulling the net down, rather than pulling tails up and out of the net. It keeps the tails tamed until you're ready.
Miku's wig is a tight fit, and it needs to be because the twintails are heavy. Try placing the bangs line where it should be on your doll's head, hold it firmly there on the parting with your non-dominant hand. Use your dominant hand to firmly grip back of the wig cap (not the hair!) and work it down over the occipital. Then you can sort of shimmy the sides into place. If you are struggling, set aside the wig, and gently soften the back of Miku's head with a blow drier or heat gun on lowest setting. Keep a far distance, and do it just enough that it's noticeably easier to squeeze. Then try the wig again. Her head will hard up again when it cools. I usually don't use heat, but it can ease the struggle if you're not used to tight wigs.
My original Miku needed her bangs trimmed. Use a reference picture and point cut the bangs to length - don't worry about making those pointy shapes. You will make the points after trimming, by using a styling product like water wax. (Miku NT's wig was already cut to my liking)
Long twintails will basically get messy and small tangles anytime that you move them around. If you neglect detangling them, the knots will get gradually worse each time you move her. So I recommend to detangle them at least once each day that you moved her. You can detangle them gently with a soft toothbrush. Starting near the bottom of the tail, hold it firmly in your non-dominant hand so it doesn't pull near the base of the tails. Detangle the tips, and work your way higher up the twintails bit by bit, until you've removed all the visible knots. If you are having trouble with a knot, you are working it too high. Start at the very bottom of the knot, work it all the way down to the tips, and slowly creep up until the whole knot is gone.
Finally, you can use the toothbrush to very gently smooth the untangled tail, and apply a styling product on the lower shaft and ends to shape and define with your fingers. My favorite product for doll wigs is Dollfie Water Wax (USA / JP). A little goes a long way, and it doesn't build up fast. It works just like a creme wax for humans, but it's doll safe. Over some display time (weeks to months) it needs reapplying. You can distribute the product gently with the toothbrush if needed - but take care to always hold the section of twintails firmly in one hand, so you don't tug the base of the tails.
Finally, if you like to brush and braid your doll's wigs, like to take your doll out and about, or even if this just seems like a lot of fuss, consider buying your Miku another wig, like one that's a little bit shorter, or vance style (clip-in ponytail).
Happy styling~
Novalyna