To add plugins on Drupal 8, follow these steps:
1. Login to your Drupal administration dashboard.
2. Go to the “Extend” page, which can be found under the “Manage” menu.
3. On the “Extend” page, click the “Install new module” button located in the top left corner of the page.
4. In the “Install from a URL” field, paste the URL of the plugin you want to install or upload the plugin’s file.
5. Click the “Install” button to initiate the installation process.
6. Once the installation is complete, check the “Enabled” checkbox next to the plugin on the “Extend” page to enable it.
Note: Some Drupal plugins may require additional configuration or setup after installation. Check the plugin’s documentation for instructions on how to complete any necessary configuration steps.