To install a theme from a ZIP file using the WordPress admin dashboard:
Log in to your WordPress admin dashboard.
Hover over Appearance and click Themes.
Click Add New Theme, then click Upload Theme.
Click Choose File and select the theme ZIP file from your computer. Make sure you select the ZIP file for the theme itself, not a ZIP containing documentation or other files. Click Install Now.
When installation completes, click Activate to apply the theme to your site.