about creating forum

Nah-mah-STAY =),

Are you familiar with the drupal core access control features? As I first comment you could achieve the feature, by

1) Creating a new user role "authenticated_user_approved" and assigning below rights to that user role:
* forum module/create forum topics
* "similar right for blog" (don't have the module installed, so I cant check that)

2) ... The site administrator could then approve then the user by adding he/she to this user group.

PS.
Role based access control can be set at http://www.example.com/admin/user/access
Roles can be assigned to users at http://www.example.com/admin/user/user

BR. Harri