Order "会议的程序与规则"；hui yi de cheng xu yu gui ze call "宣布";xuan bu call (a meeting) to order ，"我宣布大会/会议开始"。wo xuan bu da hui / hui yi kai shi

if Before the meeting ,declare this meeting open,you can say:我 宣布 开会。(wo xuan bu kai hui ) if During a conference,you want to restore order,you can say :请 保持 会场 秩序（qing bao chi hui chang zhi xu) i am not clear about the point of the remark.haha