How to Upload New WordPress Plugins
In earlier versions of WordPress, you needed to upload the unpacked plugin files to your web server via FTP. Now, all you need to do is upload the zip file you just downloaded from the WordPress Plugin Directory. Be sure you are logged on to your WordPress Dashboard.
To install the Subscribe to Comments plugin via the WordPress Dashboard, follow these easy steps:
Click the Add New link in the Plugins menu.
This opens the Install Plugins page on your Dashboard.
Click the Upload link at the top of the Install Plugins page.
The resulting page gives you an interface for uploading a plugin in zip format.
Click the Browse button.
In the resulting File Upload dialog box, you can locate the zip file for the plugin you’d like to install. In this case, the file is subscribe-to-comments.zip. Click the file to select it and then click the Open button to return to the Install Plugins page.
Click the Install Now button.
WordPress uploads the plugin’s zip file into the /wp-content/plugins/ folder on your web server, unpacks it, and installs it. The figure shows the Installing Plugin page with messages for you during and after the (hopefully successful) installation.