Log into your Netflix account and access the account page using the "Your Account" link in the upper right corner of the screen.
Select "Add Profile" and enter a name for your new hidden profile.
Click "Edit" next to the profile name. Check the box for "Private" on the profile page to set this account to private.
Sign into your new profile account by clicking the arrow next to your name in the top right corner of the page. This account will remain private with a hidden viewing history, while your primary Netflix account maintains its social features.