Acquire breasts.

Count breasts (you're aiming for 2, but 1 or 3 can work).

Talk lovingly to breasts.

Join the ABA.

Get some tops you can comfortable release the kracken (I mean, the breasts) from. These don't need to be "maternity" tops, just anything you can pull up or down enough to get a boob out comfortably.

Get some cloth nappies - just terry squares - to have under bubs when feeding, and to use for burping after feeds.

Put together your breastfeeding box - for your book, remote, Lansinoh, breastpads, snacks, waterbottle, notebook, puzzlebook, phone, pens, tissues, babybook etc. You'll spend a lot of time breastfeeding!

Maybe even borrow a box set of something ... DS1's feeds went for anything from 45-90 minutes...

Get either a breastfeeding pillow, or one of those ones with a high back, or whatever, so you can be comfortable during feeds. You may well want a pillow while they're really little, so you're not bending over to feed them - you're bringing them up to you, so you can keep your back reasonably straight.

Sleep.