Two ways to get files into your webspace:
1. The Files tab - upload straight from the browser. Archives can be uploaded whole and extracted on the server, which is the fastest way to move a large site.
2. FTP - create an account under the FTP tab and connect with a client such as FileZilla, using the server address, the username and the password shown there.
Your site is served from the public web folder of your account. Put the site's index file there - index.html or index.php - and your domain shows it.
If you are moving in from another host: upload the files, import the database under Databases, then update your site's configuration file with the new database name, user and password.