There are two choices. Check it when you check luggage, or gate-check it. Can't take it onto the seating part of the plane. When gate-checking, you'll need to get a tag from the gate people (some people at some airlines will give you a tag out in the checkin area, but generally it's at the gate), wheel it down the ramp, fold it up and leave it right before you go into the plane. They'll take it down, put it into the cargo area, and then when you get to your destination they'll take it out, bring it up, and have it there for you (if you rush off the plane you might have to wait for the stroller...so take your time deplaning).
They aren't noticing all of their peers in strollers around them?