If you have cPanel then there is in-built option which allows you to design the website in WordPress. New cPanel release has this option. There is on click options which will ask you to enter the site name, directory name, database name. You will need to enter all details correctly.
Once done then website will ready to use. For installing theme, you will need to WordPress admin panel. You can search number of themes under it. You can opt to free or paid theme of your choice. You will need to take care of the security aspect of the site. You should enable all the necessary security plugins. Also, you should not share database and WordPress admin dashboard password. You should have the adequate amount of bandwidth and resources for the WordPress site.