The process of running an APK file is different in different operating systems. As it is mainly downloaded and used in androids, let’s first go through the procedure of running it on an android device. It is often possible in android devices to refuse permission to install unknown files or applications. So, it is necessary to go to your settings and then the apps and notifications option, and then provide permission to install unknown applications. But sometimes, according to your device, it may require to give permission to a particular application separately at the time of download. If that is the case, a dialogue box will appear at the time of download and from that dialogue box, choose the option to give permission. The APK files normally open and runs on an android device without any extra tool or conversion. But if you are trying to run an APK file in a windows operating system or IOS or a Mac or any other desktop operating system, you may have to use an android emulator or a google extension or may have to extract the concerned APK file. But mostly it is possible to find a desktop alternative for any android mod APKs available.