Proper way to start with wordpress is by creating your own child theme. I found default Twentythirteen WordPress theme is very handy and easy to setup, so it will be a shame to loose any changes made after every update. Don’t ignore updates, it’s very important to be up to date. The only proper way and secure way is to create child theme.
So navigate to wp-content/themes and create new folder called twentythirteen-child.
Here you will add your custom css style and any file that you want to change from default theme (just copy original file from twentythirteen that you want to edit and change). You can copy any file except functions.php. Dont duplicate this file. Instead if you want to change functions.php create your own file in twentythirteen-child folder and add all your functions there. Continue reading How to create Twentythirteen child theme for WordPress