opt in
phrasal verb with opt verb [ I ] uk/ɒpt/ us/ɑːpt/
主动选择加入
to choose to be part of an activity, arrangement, etc.
Company policy is to leave new workers out of the pension scheme, unless they choose to opt in. 公司政策是新员工除非主动要求加入，否则不把他们列入养老金计划内。