I’m planning a trip to yellow stone national park. need advise please!!!?

I’m leaving from New York City.. so I think I should have no problem flying there. but where should I stay and how long should I stay ?

Yellowstone is a huge park. You could probably stay busy for a full week. There are many hikes some short and some long. Also there are a lot of spectacular view points.
Are you going alone or with a family? When I went it was a family trip so we rented a cabin in the park. This way we were close to everything. I don’t know where the airport nearest to the park is so you will likely be renting a car. Even just driving through the park is wonderful. Make sure you look up about any entrance fees before you go.
Have fun