While there are a large number of free and commercial FTP clients for both Windows and MacOSX users, we are familiar with Filezilla Client which you can download here.

Once you have FileZilla Client installed, you need to take the Server IP from your welcome email and enter that as the hostname you wish to connect to, on the default port 21, using the username and password you have been issued (unless you have changed the password since it was first issued!).