An APK is an Android application package. Installing one directly from a developer's website is often called sideloading. Android supports it, but you should treat the permission to install outside Google Play as a security-sensitive action.
Download the file from the developer's official website rather than a mirror, forum attachment or shortened link. Check that the domain in the browser is exactly the one you expect.
If the developer publishes a file hash or digital-signature information, advanced users can compare it before installation. At minimum, avoid copies that have been repackaged by third parties.
Use your browser's downloads list or Android's Files app to open the APK. Android may stop the installation and explain that the current app is not allowed to install unknown applications.
That warning is not saying every APK is malicious. It is asking whether you want to grant this specific source—such as your browser or file manager—the ability to request package installation.
Follow Android's link to the relevant special-access page and enable installation for the browser or file manager you are deliberately using. The exact menu labels vary by Android release and manufacturer.
Do not enable unrelated apps. The narrowest permission is the safer one.
Google Play Protect can scan applications, including some apps installed from outside Google Play. Pay attention to security warnings instead of reflexively clicking through them.
If Android reports a signature conflict, a corrupted package or an app that is incompatible with your Android version, solve that underlying problem rather than disabling more protections.
After installation, you can return to the 'Install unknown apps' special-access screen and turn the permission off for the browser or file manager. The installed app continues to exist; you are simply preventing that source from starting future package installs without another explicit change.
Download LocationOf only from the official LocationOf download page. After installation, the tracker still requires its normal Android location setup; sideloading the APK does not automatically grant GPS permission or start tracking.
Samsung owners can use the more device-specific checklist in How to install an APK on Samsung Galaxy.
Google Play is the most familiar Android distribution channel, but Android also supports direct package installation. Developers may distribute an APK themselves for testing, specialist deployments, regions or devices not served through a store, or simply because they operate their own update channel.
Direct distribution does not make an application trustworthy by itself, and absence from Google Play does not make it malicious by itself. The important questions are who publishes the package, whether you obtained it from the official source, how updates are signed, and whether the requested permissions match the app's purpose.
LocationOf is currently distributed from its own website, so the official LocationOf domain should be your starting point rather than an APK mirror.
An update is normally another APK signed in a way Android recognizes as belonging to the installed application. When the package and signature are compatible, Android can install the newer version over the existing one while preserving the app's data.
If Android reports a signature mismatch, do not immediately uninstall the old app just to force the update. First verify that both packages are genuine and that the developer actually changed signing keys or distribution method. Uninstalling can delete local application data.
For LocationOf, use the update method described on the current official download page. Old instructions referring to a store release or a historical Android version should not be treated as authoritative if the current package is distributed differently.
“App not installed” can have several causes: an incomplete download, insufficient storage, an incompatible Android version, a package conflict, or a signature mismatch with an existing installation. “Not allowed from this source” means Android has not granted installation capability to the browser or file manager you are using.
Solve the specific error rather than turning off broad security features. Redownload a corrupted file from the official site; free storage if necessary; confirm the minimum Android version; and use Android's per-source installation permission instead of enabling unrelated apps.
Samsung users can follow the Samsung Galaxy APK guide. For a security-oriented explanation, see Is sideloading an APK safe?.