BuddyPress.org

I don’t know why new users would be admin? That is not right, they should be subscribers or have no role. Even so, you can click on their name under Authors & Users and edit their role.

You can add your name to the wp-admin area by going to Site Admin > Options and typing your username (the one for loggin in) in the field: site admins.

As for the blog being created, did you do it in “Blogs” not “Users” of the Site Admin area?