Use composer to install this extension. First make sure that Magento is installed
via composer, and that there is a valid composer.json file present.
Next add our own free composer repository to your Magento 2 installation:
composer config repositories.yireo-free composer https://satis.yireo.com
Next, install our module using the following command:
composer require yireo/yireo_googletagmanager2
Next, install the new module into Magento itself:
./bin/magento module:enable Yireo_GoogleTagManager2
./bin/magento setup:upgrade
Check whether the module is succesfully installed in Admin > Stores > Configuration > Advanced > Advanced.
Done.