To take the full backup from your cpanel please follow the below steps:
1: Open the Cpanel with the login details you have received on your registered mail.
2: Under FILE section you will get an option named as "BACKUP WIZARD".
3: Once you click on it you will get the two options: BACKUP/RESTORE, you need to click on BACKUP.
4: After clicking on the BACKUP option you will get more two options FULL BACKUP/PARTIAL BACKUP, You need to click on the FULL BACKUP.
5: Once you click on it then you will get some options to fillup under "Generate a Full Backup", In Backup Destination you need to choose the "HOME DIRECTORY" and in email you need to add the email on which you want notification once the backup will completely downloaded.
6: After filling the information you need to click on GENERATE BACKUP, the backup will start generating under your home directory of file manager.
NOTE: **Once the backup will be generated under the HOME DIRECTORY you need to download it to your local system**