1. Go to your Dashboard
2. Click on "plugin" and select "add new"
   

   

   
   
3. Here you can search your add-on or check the new plugin
4. Once you have find your plugin ,click on "Install now" and confirm with "ok" button
   

   

   
   
5. Wait for the installation then "activate" the plugin with the "ok" button
   

   

   
   
6. You can go to "Plugins" to manage your plugin and instal or desinstall it
   

   

7. Depending on the Plugin, you can have some configuration to perform (in the plugins page or in the tools page).