The documentation is outdated much. I was actually planning to propose updates to it myself, but Bottles slowed development and few weeks ago Bottles Next was announced so you’d need to rewrite the documentation once again when it drops.
Yes, you must create a new bottle and then you will have an option to use installers. It’s on the first window after entering the bottle - “Install programs…”
And oh, that’s a pity. FL Studio worked flawlessly, so I was really looking forward to other automated installers for games, VSTS, and software to be added by smart people. It seems like Bottles Next is a long way off.