To add a new theme to your WordPress installation, follow these basic steps:

1. Download the theme archive and extract the files it contains.
2. Using an FTP client to access your host web server,
3. Upload the theme files to: wp-content/themes/

Adding New Themes using the Administration Panel:

1. Log in to the WordPress Administration Panel.
2. Select the Appearance panel, then Themes.
3. From the Available Themes section, click on the theme title (or theme screenshot) for the theme you wish to activate.
4. A preview of the theme will be shown.
5. To activate the theme click the Activate “Theme Name” link in the top right.
6. Your selection should immediately become active.