Plugins allow you to add additional functionality to a WordPress site.
If you go to the Plugins section in the admin panel lefthand menu (under Appearance), you can access the vast WordPress plugin directory, and can search for a plugin by name or features/function.
Helpful tips: when trying to determine which plugins to use, look at when the plugin was last updated, how many people use it, and what its rating is (and how many people rated it). Obviously, more recent updated plugins, as well as those with higher rankings and thousands of downloads are more likely to be reliable than old plugins with a handful of users. You will also want to try to find plugins that were tested with the most recent version of WordPress; if it hasn’t been, it may still work, but there are no guarantees.
In my experience, doing some research is the best way to find a plugin that will work for you. When searching, read all the documentation the developer made available, and go to the developer’s plugin site if possible. Even better, get recommendations from other WordPress users.
Installation is a two-step process. First, click “install” on the plugin page. Then back in your admin panel under plugins, you will then need to activate the plugin.
Some plugins work right away, but many will need additional information from you. Look for their settings on the plugin page itself or in a menu item in your admin panel. Some plugins will make their own admin area, while others will have their settings located in the appropriate section of the admin menu.
I’ve written two posts suggesting plugins you might find useful:
Essential WordPress plugins for new sites
More fun with WordPress Plugins
If you recommend additional plugins or have requests for specific functionality, be sure to note it below!