S~How To Disable Preferences

Managers have the ability to choose whether employees can enter availability preferences or not.  They can turn on and off the Preference tab for the entire account.  (This impacts the account as a whole, and is not directed at specific employees.  All employees can either enter preferences or not, depending on the permissions set.)

If you do not want your employees adding their work time preference information, you can use the Settings>Global Employee Permissions page to restrict them from being able to enter their prefer & dislike times.  That way the employees cannot see or edit any preference information you may have added for them.  More: http://mgrhelp.when2work.com/h-sub-settings/h-co-settings-emp-perm

Note that you can allow employees to enter their own preferences but just ignore those preferences when you are assigning shifts by hand or by AutoFill. So even if there are preferences added for your employees you can simply disregard that information when assigning your shifts. More: http://mgrhelp.when2work.com/h-sub-settings/h-co-settings-emp-perm

This might be preferable as even if you don't use that information it might be nice to have access to it when looking for a replacement etc.