Go to Settings → Security → Unknown Sources and enable it.
(or Apps & Notifications) and allow installation from "Unknown Sources". Download & Install: kingroot apk version 8.1.0 download
With newer versions like 9.0 and 10.0 available, you might wonder why anyone would download version 8.1.0. Here are the compelling reasons: Go to Settings → Security → Unknown Sources
Allows the uninstallation of pre-installed carrier and manufacturer applications. kingroot apk version 8.1.0 download