All plugins that you have a license for will show up under the tab My plugins. The uninstalled plugins are at the top under the Not Installed section.

To install and authorise a single plugin, select it by clicking it and then click Install.

To install and authorise all uninstalled plugins in one go, select them by clicking Not installed in the bottom banner, then click Install.

After installation your plugin(s) will show up with a green underline under the Installed section.