If your nipples are flat, it may still be possible for your baby to latch. If that happens, your baby’s sucking action should draw the nipple out enough. Another method you could try is to pump a little breast milk before you start breastfeeding. This usually makes it easier for your baby to latch onto your nipples.
Breast shells are a method you can try during pregnancy to help draw your nipples out, or you could try breast shields which fit over the nipple and act like a teat. There are also special exercises you can do to help your nipples become more prominent. If you find yourself a lactation coach then she can teach you these exercises and other methods to make breastfeeding with inverted nipples possible and comfortable for you and your baby.