It's a good idea to install it on your computer first and have a play around with it before going live. It's easy to do, luckily. You can install XAMPP (for Windows) or MAMP (for Mac), each of which is a ready-made local server environment. Then you can install WP and have some fun with it.
You can just use the default theme for WP and learn to manage it from the control panel. Gradually read through the docs at WP to see what can be done with it. If you know HTML, CSS, and a tiny bit of PHP, you can start to create your own themes etc.