As of February 2020, for Android Studio 3.5.3, the simplest answer I found is this video.
Note 1: At 01.24 "Find" tab appears below. Click "Do Refactor" and continue as in the video.
Note 2: If you have any Java/Kotlin files "Marked as Plain Text" you need to modify the package name at the top manually, i.e. package com.example.thisplaceneedstobemanuallyupdated
Note 3: Be careful about letter cases while renaming, just as in the video.
Note 4: If you want to update the project name on title bar of project window, modify rootProject.name = 'YourProjectName'
inside "settings.gradle" file under "Gradle Scripts" directory.