You can do this by simply right clicking the element on your website you're trying to edit, then clicking “Inspect Element”.
Once you click that, an elements section will show on the bottom of the window. The element sections shows you all the elements of your website. Simply hovering your mouse over an element highlights that element on the website itself. You can double click the ID or Class property and copy it to use later.
On the right hand side you can see properties assigned to the selected element. That part is useful to test your css rules and see the changes it will make without changing the site itself. Simply click on a matching rule and type in your code, changes will show on the site automatically.
