。
Leave it on the voicemail, OK?
Literal
Voicemail [to-に] put-in [preparatory-といて] [agreement-ね].
留守電 is a casual abbreviation of 留守番電話 (answering machine). 入れといて is a triple contraction: 入れておいて → 入れといて. The ておく (do in advance) pattern is heavily contracted here — very natural in casual speech.