We would always recommend taking a full backup of an account before completing any potentially breaking change to your site. This is the single best way to backup the account as it will take absolutely everything and package it and compress it into one single file. To complete this you would:
Log in to your cPanel: www.YOURDOMAIN.com/cpanel
Click on Backup Wizard
Choose Backup
Choose Full Backup
Leave the backup set to home and insert the best email address to reach you in the the second field.
Click backup. This will take time to complete and the server will email you when the backup is complete.