My first theme developed for WordPress.

Copy the release ZIP file to your wp-content/themes folder.

After locating it there, extract its contents.

The folder containing the "MyTheme" theme files will be extracted.

In your WordPress admin panel, go to Appearance/Themes, select the new theme, request a Preview to make sure it's working. If so, you can then select Activate, and the changes will be applied to your site.