I go to wpForo Usergroups. Below are the screenshots (attached one by one). Please let me know what's the problem. Thanks.

Hi peterwangbiz,

Make sure you're admin in WP and in wpForo, then do a bit more scroll down and find this option:

Navigate to Dashboard > Users > All Users admin page, edit the current user and you'll find the option.

The screen I saw is different (in case I made the wrong setting, I've re-intalled the WordPress and wpForo). Please have a look at the screenshot attached. Thanks.

@peterwangbiz, could you please click on that user Edit button, or just click on the Your Profile menu under the users Menu section in left black sidebar? Your screenshot is the User list, this is not the Edit user Screen.

could you please click on that user Edit button ------ follow your way: I've registered a new member and then click it's user Edit button, then I saw a screen very similar to yours (attached), but still a little different: no Moderator option there, please have a look, thanks.