Go to My downloadable products. The file that you download normally is a zip file.
Use FTP client (such as Filezilla, WinSCP, cuteFtp) to upload or copy all folders in the zip package to your Magneto site root folder. This will not overwrite any existing files, just add new files to the folder structure.
Open Command line in folder root of Magento and run following command respectively:
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy -f
php bin/magento indexer:reindex
php bin/magento cache:flush
Navigate to Stores/Configuration, if you can see the extension tab, it is installed properly.
