Installing custom WordPress themes is executed directly through the WP-Admin dashboard interface or by uploading extracted theme files to /wp-content/themes/ via FTP.

WP CLI Theme Installation Commands

WP CLI Commandsbash
# Install theme from official repository via WP-CLI
wp theme install twentytwentyfour --activate
 
# Upload and activate custom theme ZIP file
wp theme install /path/to/my-custom-theme.zip --activate