Yes, you can change WordPress before installing on your own server. Better install WordPress in your computer under localhost (install XAMPP), use it, decorate it and then transfer to your web server. Wish you all the best.
i think you want to install a local server on your computer. if you are a pc user, please just follow up the instruction to install XAMPP, it's quite easy. comment on the post if you need any help. How to Install WordPress on Local Server with XAMPP Added: if you use Mac, try MAMP.