4 answers
An Admin should go to your profile then object settings and ensure your the tab is listed as hidden.
If you have never been able to access contracts tab when you log in then your administrator needs to add at least "read" access to your profile CRED or create a permission set for you.
Tab settings
https://help.salesforce.com/HTViewHelpDoc?id=permissions_tab_settings_ref.htm&language=en_US
Once you have access the + sign at the end of tabs will allow you to add the Contracts to your app.
Hope this helps!
Meg
