There is only one way to install:
Upload packages from this website. Go in your Joomla administrator panel, choose the menu Extensions -> install/uninstall . Select packages by clickling on "upload and install" button.

To upgrade, all custom rules are preserved instead points to users. No needs to uninstall the previous version. Just install the latest version, then go to in admin panel, check and save the general configuration if new settings.

If you want uninstall the previous version before, just uninstall and install the latest version, then go to in admin panel, check and save the general configuration. Go to in menu manager and edit each menu linked to AlphaUserPoints and save again.