[leaabc123]

You can fly up to age 2 and holdthe baby in your lap although it isn't recommended. I have seen many folks with car seats. Your car seat must have a sticker on it that says Approved by the FAA (usually in red letters). Most newer car seats have this automatically so you don't have to buy a special one.
If your seat is older (say a hand me down), then you may have to purchase a new one.

When you booked the seats, you should have said one seat was for an infant. Babies and children cannot sit in emergency exit rows and they usually like the car seats to be installed by the windows. If you didn't say so in advance, just call back and let them know.

Most airlines will allow you to preboard with an infant. You can also gate check your stroller so you don't have to hold the baby when walking around the airport. certain airports will let you go through a special screening line as well, with an infant.

Good luck and most of the time, the staff is more then happy to help.