Flying ants get inside your house through tiny holes and spaces that you may not notice exist.
The flying ants may also come into your house when you have a door or window open as well.
To eliminate flying ants around your house look outside for any ants nests including flying ants nests and pour some boiling hot water down the ant hill which will kill the ants.
You should also pour some dish soap first down the ant hill and then follow it by boiling water since the dish soap will ensure the ants are killed first.
You can also spray flying ants inside your house using dish soap to kill them and set out sticky traps or sticky tape to catch the flying ants.