If you are going to manually back up your website files, the first step is to log into the Control Panel. When you set up your account, your hosting provider will have sent you an e-mail with a link to this, along with a username and password. The information contained within this e-mail is important. Ensure that you keep it secure, as it's required to gain access to your website and can potentially be used to exploit your site. It's a good idea to copy and save the information in a separate file, away from your site files as well.
The link to the Control Panel should look like this:
Copy the link provided into the browser window and type in the username and password as prompted.