To use a shortcode, you just paste it into any WordPress page or post. Instead of pasting it, you can type it. (If you use WordPress 5.0 or higher, with the new Gutenberg editor, see this instead.)
For example, to use the birth report shortcode on a WordPress post, type the shortcode into the editor:
Visitors to your site will not see the actual shortcode. Instead, they will see something that replaces the shortcode. For example, when you use that shortcode on a page, your visitors well see the birth report form. Every shortcode does something different.
You can also add other stuff on the page, either before or after the shortcode. Here is an example that has some introductory text first, and then the shortcode.