You will need an FTP client to do that. Some of the most commonly used FTP clients are:
Once you have downloaded your FTP client you can open it up, and connect to our FTP host using the following information:
Hostname: ftp.yourdomainname.com
Username: This is your FTP username
Password: This is your FTP password
Once connected, download all your files onto your computer. Please ensure your files are easy to access. Then you can have peace of mind. If something goes wrong with your website, you will still have backup files to help you put your website back up on the Net in no time.