Shipped eggs are fiddly but can be a wonderful experience. Bringing in varieties and genetics otherwise unaccessible. Here's a few pointers.
Buy eggs as close as possible to your location. I try to stick to seller under 1000 miles from my location. It sounds like you've already purchased your eggs but it's worth mentioning for next time.
Use the best incubator you can. I might have missed where you mentioned what you're using but shipped eggs really need a consist 99.5 temperature.
As for air cells I've taken to adding a 2-4 similar sized local fertile eggs into the hatch with the shipped eggs. These are the ones I monitor air cells on. I find it's easiest to make them while candling on their sides. I mark when they go in the incubator then days 7, 12-14, and 18/19. I adjust my humidity (a tool to affect weight loss) based on these local eggs.
Shipped eggs are prone to late quitters. For some reason new hatchers seem to miss this and think if they get development they're out of the woods. Not so. For me development= cautiously optimistic.
Incubating and hatching upright should be considered with shipped eggs. There are pros and cons of both methods. This is where hatching becomes more like art and less like science. You'll have to read about the nuances of both ways,which you're already doing, and decide what works for you. If air cells are wonky I've had slightly better hatch rates with upright incubating/hatching. Like an extra chick per dozen eggs I set. Not much but noticable to me since I hatch 2-4 batches of shipped eggs a year.
Depending on your location you'll want to add "call for pickup" on the egg package. Not all sellers do this automatically. Then you'll pick them up immediately when your post office opens. This saves the eggs that last leg of delivery. Which in my semi rural area is pretty rough.
If you haven't hatched any eggs before you're not doing yourself any favors by starting with shipped eggs. Ideally you'd do a test batch of local eggs to figure out your incubator and best humidity for your area. That said hatching eggs of any kind is always a exciting and worth doing. I'm excited for you to get your eggs and jump right in. Happy hatching!
