Hi,

As I see you're using Vertical Navigation - so, you need to move mouse on the vertical navigation to make it can be scroll down - It's not a sidebar

If you're looking for a sidebar display right on this page: https://999x666.com/category/%e7%b4%ab%e5%be%ae%e9%99%bd%e5%ae%85%e9%a2%a8%e6%b0%b4%e5%90%89%e5%87%b6%e8%a9%95%e9%91%91/

You can go to Customize > General Options > and check to "Enable Sidebar on Homepage"

Best Regards,

PenciDesign