Step 1: Click on your profile/picture found on the top right corner of the forum
Step 2: Click on the third option, "Privacy Settings"
Step 3: Once in the Privacy Tab, you will see 'Online Status', 'Show Scrapbook', 'Show Slambook', 'Show Testimonial'
Select the option you want and press the red "Update" button
at the bottom to save your preferences.