in your admin.ini you'll see a whole bunch of constants defined with integer values. set it to 1-4 to determine which levels can use it.
if you mean what level the character is (not admin level) then you could add that into the 'else if' statement. example for the 'board' command:
else if (command.length() >= 2 && command.compare(0,2,"bo") == 0 && this->player->character->admin >= static_cast<int>(this->server->world->admin_config["board"]) && this->player->character->level >= 10)
the bold part would be what you add to make sure that people were level 10 and up to use the command (who were also admins).