Please HELP back partition missing

Please help . I set my MAc to be a hard drive and and a back drive both icon were on my desk top. Now my user name and password were know to al the family and my son has dragged the back up hard drive icon to the trash and put in the password... I have since changed the password but how do i get this icon back to access the back up files as it's not in the trash
Please help
Nic