First time adding fruit/berries to primary (Question)

I was told to add my berries to the primary (3-4 days into the primary) after cleaning them by boiling some water and letting them sit in it for a few minutes to kill the nasties.

My question is, how do I add them to the primary without introducing air?

I'm assumeing I just take the stopper/vent off the top and drop them in, that not much air will get into the jug.

I purposely left 1/2 gallon out of my batch in order to make room for the displacement of the berries so room is not an issue.

The wort is still actively fermenting and producing CO2 so the worries about introducing air are little. Just drop them in.

What kind of beer they going into?

I have a (Brewers Best) Red Ale kit I got locally and I'm dropping Rasberries into it.

I understand from the guy I talked to that it will be very red after the berries are added. hahaha