If you are using a version of windows without MS store, installing Store apps (.appx) is a manual process. To ease the installation, an app called App Installer is used to install an .appx app file. App installer has to be installed manually via powershell, after that you can install other .appx by App Installer.
Steps
Go to "https://apps.microsoft.com/store/apps"
Search “App Installer” and copy the browser link.
Go to "https://store.rg-adguard.net/" and paste the link and choose “Retail” in menu right to it.
Download the latest file with .appxbundle format, for example
(to download right click on link and press “save link as” and save them in Desktop folder).
Open powershell in the folder that the files are in (Go to the folder and press Alt+F+S+A) for Administrator installation. If you have a seperate user space, just open normal powershell, type “cd desktop” to go to desktop directory.
Now to to "Settings->Apps->Apps&features", see if App Installer is present. If it's present, all the tedious process is completed.
To install another app, follow step 1-3 and download only the latest “.appxbundle”. After that open the directory in which the ".appxbundle" file is stored and in file explorer go to View and check File name extensions then double click the file and an installer will open.