You can create a backup of your site quite easily. Account backups can be performed using the cPanel -> Backups functionality for your hosting account. If your account is not too big in size (under 5000MB) you can perform a full account backup just with one click.
To create a full cPanel backup of your account, press the Download a Full Website Backup button.
A new page will open on which you can set the location of the newly created backup and configure an email address on which to be notified when the backup is completed.
To start the generation of the backup, click the Generate Backup button, the automatic backup creation will start, and you will be notified on the email address you specified when the backup creation is complete. After that, you could find the backup archive in the folder you specified and download it.
If the account is too large (over 5000MB) for the full automatic backup, the files and the databases should be backed up separately.
In this case, you would need to know what your web site consists of and thus what should be backed up/restored. Sites consist of files and databases. You must make a backup of them all if you want to have your site exactly the way it has been before.
How to backup/restore your files?
In order to back up your files, you should download all the files from your public_html folder to your computer using your favourite FTP client. After that, you can upload the files to your hosting account and your website will be restored.
How to backup/restore your database?
Once having all the files on your computer, you should make a copy of your MySQL database.
You may also request an affordable backup creation of your whole account by posting a support ticket.