The master administrator (the one created when sytist is installed) can create additional administrators to log into the admin. The link to the administrators section is in the upper right hand corner of the admin pages.
When creating an administrator you have the option to give them full access to the admin or limit what sections they have access to.
If they don't have access to a section, they will not see the option for that section in the menu.
This section is also where you can change your password.