* You may need to install "File Manager+" after factory resetting your tablet.
Start "browser" app and use this link https://www.apkmirror.com/apk/file-ma...
to download the File Manager + apk file. And install it.*

this video is showing how to install the de1app and the update app on the tablet. If you bought a new 3rd party company's tablet, you need to install the app own your on. In this way, you don't need to connect the tablet to the computer to install the app.

Also, if you watch from 4:37, you can see how to restore the app when you accidentally deleted the de1app from the tablet main page.