How to upload aab file which is 1.6gb to the Google play console?

As Google play change its policy from August 2021 , now there is no support for apk and obb files. It supports only the Android app bundle. But it has its limitations for size and we can’t upload obb files too.
My aab file is now 1.6gb so I’ve to use Google Play asset delivery. In that there are three methods which are install time(1gb allowed), fast follow(512mb allowed) and on demand(multiple 512mb files allowed)
Now by default if you enabled the Google PAD plugin in ue4, the install time will generated automatically.
Since my aab is 1.6 gb, I have to use more than install time, but I don’t know how to setup fast follow and On demand for ue4.
So could somebody help on this?

Generate a obb file separately and find a way to add it inside the game in android. Lile the big titles do.
Fortnite downloads 6gb after installing the apk.

I couldn’t find a way to add obb inside the game but I found a way to reduce my game size under 1Gb, so now the obb will be included automatically in install time delivery