If you have purchased your domain through ASH HOST, then you can use ftp.yourdomain.co.nz as the server name for your FTP program.
If prompted, you should also include the path /public_html/
Your username will most likely be your cpanel access username and is provided to you upon creation of your subscription. (Note: often you will have access to your control panel prior to your subscription being provisioned)
If you have not purchased your domain through ASH HOST, or if you have not updated your DNS, then you can upload to your hosting using the IP address of your server. (Please be aware that these are subject to change and if you have any issues you should contact customer support)
To identify your servers IP address simply log into your Control Panel and go to the System screen for the particular hosting you wish to upload to. The IP address is listed next to the Hosting heading.
For Example: Hosting (Domain has physical hosting on IP 188.8.131.52) In this example you would use the numbers: 184.108.40.206 as the ftp server name.
IMPORTANT NOTE: Please ensure that you upload your files to the httpdocs folder.