have a dreamLiterally means “see a dream.” With いい夢を見てね, it means “sweet dreams”; in other sentences, 見て is the te-form of 見る and connects to what follows, often meaning “having a dream” or “after dreaming.”
JA: 昨夜、怖い夢を見て眠れなかった。
EN: I had a scary dream last night and couldn't sleep.