Summarize this article in one sentence.
It's usually a button with a grid of dots ⋮⋮⋮ at the bottom center of your screen. Most of your files will be organized into folders. Most versions of Android have a stock File Manager app. If yours doesn't, go to the Google Play Store, search for File Manager and download one of the available free apps.

Summary:
Open your device's Apps Tray. Tap File Manager. Tap a folder to browse the files inside it. Tap the magnifying glass icon to search for a file.