Only one hard disk partition is visible ...

Hey, in fact I am new user of Linux and I am used to windows, then when I installed the new Operating System Kali Linux , I had problems with partitioning the disk and I choosed the guided partitioning option. Once the installation finished, I can find only the disk which contains the Operating system. I tried in the terminal the command fdsk -l but the response is
fdsk: cannot open /dev/sda: permission denied
fdsk: cannot open /dev/sdb: permission denied.

I really need your help. I don't know what to do