If you want to develop the theme on your local computer, it’s very important to make sure you have a local server configuration is complete. There are four popular local servers such as MAMP (Mac & Windows), WampServer(Windows), XAMPP(Windows, Mac, Linux), and Varying Vagrant Vagrants(VVV – WordPress specific Vagrant configuration for Windows, Mac, Linux).

After you setting up the local server, the first thing you need to download the WordPress core files from this URL https://wordpress.org/download/ on to your computer. Remember the exact path where you installed the WordPress core on your hard drive.

In the root WordPress folder, there are many files with extension of php and prefixed wp- files, these are the part of WordPress core files and you don’ t need to touch them. There are three folders named wp-admin, wp-content, and wp-includes in the main folder.  We are only going to access the folder named wp-content, all the themes and plug-ins located in this folder.

Next, you need to create a folder and you name it whatever you like, this name going to be the title of the new theme. I’m going to title it ‘myNewTheme’. This new folder should be located in the themes folder that is located in wp-contents folder.

In myNewTheme folder, you need to create files named index.php and style.css.

And you can type “Hello World!” in index.php and style.css.  In the style.css  you can type this:

/*

Theme Name: myNewTheme

Author: Smith Wooden

Author URI: https://www.yourwebsiteurl.com

Version: 1.0

*/

as an example and save it.

And then go to Dashboard of WordPress backend and click Appearance and select Themes, you should be see your new theme. Active the new theme and you should be see “Hello World!”