You can click on the directory to go straight into its folder in the cPanel File Manager




To change the root folder just click on the pen icon at the edge of the document root. Please don't do this unless you know 100% what you're doing. This change should only be made by an experienced web developer as if it's incorrectly used, it can easily break your site and make it inaccessible

Once that's done, you will see this pop-up box. Edit the Document Root field and hit the Change button.

Doing the above for addon domains is similar. First click on the Addon Domain icon in cPanel

Here you will see the same options as in the Subdomains screen and you can access or edit the root folder in the same way