If your hosting accounts are not automatically listed, then Click on Services -> My Services and all your Hosting accounts will be listed along with any other products you have with us such as Domain Names for example.
Find the account you wish to check and click on the ACTIVE box where you will be taken to that hosting accounts individual detailed page.
On the new page, it will show the hosting package for the hosting account you wish to check under Package/Domain so you can be sure you are administrating the right package. Then on the right hand side see "Usage Statistics" where it shows your current Disk Usage and Bandwidth Usage for that individual hosting account (please note that due to the rounding up/down of various services and the way files are stored these figures can vary slightly from other calculation tools and is intended as a guide only).
If you need to see a break down of your disk usage so that you can better understand where your total usage is coming from, this can easily be seen by logging in to your cPanel, by visiting :-
and then selecting Files and click on the button "Disk Space Usage".
This will show a break down of your main root directories such as mail, public_html, mySQL databases, logs etc.
You can then scroll down further to a detailed breakdown and have two options.
1. Expand the directories by clicking on the [+] symbol next to the specific directories and sub-directories to see what individual folders and/or subfolders are using.
2. Click on the folder name (e.g. public_html) and it will take you to the file manager to give a breakdown of all the files in that directory.
In the file manager you can navigate around all folders/sub-folders and rename, delete files etc.