If you wish to Enable a plugin, simply:
- Log in to you site
- Go to Dashboard -> Plugins -> Plugins
- Click on the Activate link found under the desired plugin's Action column. (NOTE: A Deactivate link will be present if the plugin is already activated)
- Click on Dashboard. Your plugin should be installed now!
To Deactivate a plugin, go to the same page where you activated the plugin and click on the Deactivate link that has now replaced the Activate link.
Pro tip: Only activate plugins you are using; fewer active plugins generally means a faster site.