how do i execute command prompts?
The linux equivalent of the DOS "command prompt" is called the "shell" or "terminal". Look for it in the menues.
To log in as superuser, type "root" for the username followed by the root password.
When you are looged in as a regular user (the normal way you log in) you can still use superuser stuff via the "su" (switch user) command or the "sudo" (switch user do) command entered in the terminal.
Try "man su" for details.