First off, you will have to decide how much you have to invest, and how many plants you want to grow. I would divide the area into 2 sections, The Veg room, and the flower room. You will need about 1/3 of the space for vegging, and the rest for flowering.
Depending on where your window is, try to have access from both rooms if you can for easier ventilation. For a wall dividing the two, consider framing it, and then using "panda film" (plastic sheeting, one side white, the other black) available at grow stores. You could just put a sheet the size of a door to use as an entrance between the two areas.

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