Don't open the incubator until the rest have hatched. The first one can stay in there for 24 hours. Probably longer. I usually take them out at about 24-30 hours. If you still have some that have pipped, but not hatched, act quickly so you don't lose too much humidity. Toss some sponges or a few lightly scrunched up wet paper towels in there to spike the humidity back up. Eggs that haven't hatched before opening the bator can be kinda iffy after you open it, so wait as long as you can before doing so.
I once took my bator into the bathroom, turned on the hot water in the shower until the bathroom steamed up, then opened the bator and took out the hatchlings out. That seemed to keep the humidity up, but that's quite an operation and I wouldn't do it unless you have to spend a lot of time taking out a lot of chicks.
UGCM