Help me save my Valentine Day orchid!

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I bought this beautiful plant on Monday. It is about 2 feet tall including base. After just one day of having the plant the petals are getting green spots and it seems decaying. Some petals are also really soft, not firm how they were when I got it. I haven't watered it yet because the soil is still rather damp. I have it in my window all during the day, however since I am in Iowa and it's winter there is a constant over cast and the flower has yet to see the sun.

Here is what I am working with right now. Any help would be greatly appreciated. I do not want to have to throw away this $40 plant before my girlfriend can even see it, and I want to give her a healthy plant. Thanks again.