When a master owner adds localized copies, that owner has the option of including localization instructions for the copy owners. Those instructions (if the master owner included them) are added to the email you receive notifying you that you've been assigned to own and localize a copy.
You can also see at least part of the instructions in My Tasks.
You can always access any included instructions in the copy document's Properties Wizard.
Note: If the Instructions box is empty, then the master owner did not include instructions for this localized copy.