The answer has already been given.
Either use Powershell to hide the field in Display Form (take a look at another discussion for some helpful guidance or at this page)
#Get the web and site column objects
$web = Get-SPWeb http://site
$column = $web.Fields["Column To hide"]
#Set the PushChangesToLists property for the changes to be applied
#to lists where the column has already been added
$column.PushChangesToLists = $true
#Change the ShowInEditForm and other properties and update objects
$column.ShowInEditForm = $false
$column.ShowInNewForm = $false
$column.ShowInDisplayForm = $true
£column.ShowInViewForms = $true
Or Use Sharepoint Manager which is an essential tool for Sharepoint anyway and since it has a Graphical User Interface it is great for beginners too.