Basically you need to go to the backend of the website, login and hover your cursor over extensions. From the drop-down choose ' Install/Uninstall '. Before we proceed with the installation we need to make sure that we have set the write persmissions for all the folders required in the installation process. For this open a new tab with the administration link and go to 'Help->System Info->Directory Permissions', a list with all the joomla directories will appear.

You need to have the following setup:

For installing a joomla component you need the following folders to be writable:

  • administrator/compoenents
  • administrator/language
  • components
  • language
  • tmp

Some components has there own plugins or modules so make sure the following are writable also:

  • modules
  • plugins

To install a joomla plugin you need to have:

  • plugins
  • tmp
  • language

For modules you need:

  • modules
  • tmp
  • language

For a frontend joomla template:

  • templates
  • tmp
  • language

And for a backend joomla template:

  • administrator/templates
  • administrator/language
  • tmp

After you verified that you have the above setup you can proceed with the installation. In the tab where you got to 'Extensions->Install/Uninstall' click browse (Firefox) or Choose file (chrome), select the desired extension and click 'Upload file & Install'. If there were no errors you should have your extension ready to work for you.