WordPress is very good about helping you keep everything up to date. Take a look at the admin bar in your WordPress site. You’ll probably see something like the image below.
On the top, just to the right of the site name is a little icon with a 6 next to it. That means that there are 6 updates that WordPress knows about for plugins and themes on your site, or WordPress itself. The little 6 means the same thing.
To update, click either the circle arrows or the updates link under Dashboard and it’ll take you to the update page. From there you can pick and choose what updates to do, although you should probably do them all unless you have a specific reason not to.