In order to create tar.gz/zip/rar/tar.bz backups follow these steps:
1. Log in your cPanel and go to the File Manager;
2. In the left box, navigate to the directory / files you'd like to archive. Mark the items to be archived in the left box and choose "Compress" from the top menu.
If you are having problems with compressing your files/folders, ask your host for assistance. SiteGround provides the best cPanel hosting and we will assist you with any cPanel-related issues you may have.