U should make your Admin config on database.
Find your login user name and change him access to admin by using that thing :
mysql> SELECT user_id FROM jforum_users WHERE username = 'username_of_your_admin';
mysql> 5; (suppose it returned 5 here)
mysql> SELECT group_id FROM jforum_groups WHERE group_name = 'Administrators';
mysql> 3; (suppose the id of the Administrators group is 3)
mysql> INSERT INTO jforum_user_groups (user_id, group_id) VALUES (5, 3) [originally posted on jforum.net by kadirbasol]