Problem in theme installing?

Log in to your server via SSH, upload the zip file to the /var/www/html/wordpress/wp-content/theme/ directory, then extract it. If you have a control panel, upload and extract the theme using the control panel file manager.

Once finished, go to WordPress administration back-end and activate the theme.

If you have SSH access to your server, check the permissions/ownership of /var/www/html/wordpress/wp-content/theme/ directory.