You can say: 잘지냈어요 ? Chalchinaesseoyo? And you can say: 어땋게 지내셍요? Eottokae jinaeseoyo?

since you're a beginner in korean, i'll just give u romanizations.. you may use "annyeonghashimnikka?" "chalchinaeseoyo?" = Have you been well/good? but you can still use this too

잘지냈어요 ? chal chi nae seoyo

Asking "How are you?" as a greeting is more of a Western thing. To ask this in Korean is more of asking how they are health-wise (At least to my knowledge).