Manual plugin installation via FTP client
This approach is for a little bit more advanced users who already have idea how WordPress works and what its folders structure is. Why I am saying this is because if you upload your plugin in a wrong location, it will never work.
Here is an example for manual installation:
Open your browser and type WP Super Cache. The first result you will see is this one :
Note this is link to the official WP Super Cache page. On that page you will see a big orange Download link on the right. To download the plugin, just click that button. When the process is finished you will have a new file in your Downloads folder named wp-super-cache.1.4.7.zip. Depending on when you read this tutorial, the version ( 1.4.7 ) might be slightly different because the developers may release a newer version. The next step is extracting the content of that ZIP file into a new folder preferably named wp-super-cache.1.4.7. Inside it you will see another folder named wp-super-cache and this is the folder that you have to upload to WordPress plugin folder that is located on your hosting account.
When done, open your FTP client and connect it to your hosting account. After that browse wp-content folder and then plugins and finally upload wp-super-cache there. Here is screenshot that shows the process
Now let’s go back to wp-admin section and check the plugin. If everything is fine you should see WP Super Cache in Plugins section as shown below:
As a final step you have to activate the extension. Note that depending on the extension you install you may need to apply some additional settings. In this case upon WP Super Cache activation, additional menu will appear. Its location is in Settings menu on the left column, so click Settings and you will see WP Super Cache at the bottom. Now click WP Super Cache and set up the plugin the way you want.