User registration is being processed through the default WordPress registration system. If you already have a registration approval function in WP then it’ll work for wpForo. If you don’t have such function please search for Registration activation plugins, they should work for wpForo too. These are two good examples:
I'd also suggest you check out Robert's answer in this post:
What if I also wanted to ask some additional questions on the registration form?
Please check out wpForo – User Custom Fields add-on:
You can create custom Registration form with custom fields, add custom fields in User Profile system and in Members Search form. All forms and areas can be easily created by form builder tool, you can set rows and columns. Once the layout is ready you can fill form columns with custom fields. Each custom field can be displayed/hidden based on current user usergroup permissions. More info in documentation: https://wpforo.com/docs/root/addons/wpforo-user-custom-fields/