Thanks a lot for reaching out. Are you trying to do this on a smartphone?
If so, select "SafeGuard" and then flip your phone to to landscape mode, the options to block particular categories / websites will then appear on the left hand side.
Thanks for getting back to us. If the safeguard options to block or allow a specific page isn't showing then I'd perhaps go into options on the browser you're using on the phone and pressing the "display full desktop site" option as this should reveal any of the missing options for you. Let us know how it goes.