This is because prenatal classes at hospital prepare you for the first few weeks. Also help from midwives.
Various health checkups are a chance to get more advice. There are various phone lines etc.
I've had 2 kids. First one we read a week by week book for about 2 weeks and that was about it. Second one nothing at all.
Humans have been doing this for thousands of years. A lot more than you think will be instinctive. Good luck and congrats!
Additionally, suggest reading up on Polyphasic Sleep-- in order for YOU to survive the first several months, build naps into your schedule > http://fourhourworkweek.com/gear/#uberman
"The Happiest Baby on the Block" was a good practical guide - https://amzn.com/B00TCI48AE
Another book that was great "the happiest baby on the block" for those first three months.