Plugins are like apps for your WordPress site. They allow you to add additional features like contact forms, photo galleries, etc to your website.
To install plugins, first you need to visit Plugins » Add New page in the WordPress admin area. Next, you need to search for the plugin you are looking for by typing in keywords (like photo gallery, contact form, etc).
If you know the name of the plugin that you want to install, then you can just enter the name of the plugin.
In the search results, click on the install button next to the plugin that you want to install and WordPress will install it for you.
Next, you will need to click on the activate button to start using the plugin.
You can also install plugins sold by third party developers. Those plugins come as a zip file.
Simply head over to Plugins » Add New page and then click on the upload button.
Next, you need to click on the choose file button to select the plugin zip file from your computer and then click on ‘Install now’.
For more detailed instructions, see Lesson 17 on how to install a WordPress plugin.