iOS making a new project for an existing app

I'm remaking from scratch an app that was previously in Objective-C, to Swift. But I'm not really sure how can I make the new project be linked to the app that is already in iTunes Connect. What I mean to say is that I have a new project whose binary is supposed to be uploaded as the binary of the already registered app.

Besides using the same Bundle Identifier, what else do I need to do to achieve this?

PS: For some reason, the new project won't let me change the bundle identifier's last part: the old one was com.example.myproject while the new one is com.exmaple.MyProject (the new one has capital letters). When I click on the text box to change it to lower case, the MyProject color change to gray and I can't delete it