Brush it every day. Wash it now and then. When it gets frizzed up, use a spray bottle to wet it, then flat iron at a low temperature, then brush the section. Repeat. For more thorough detangling, put your wig on a wig stand and use a fine-tooth comb, rather than a brush.
I'm pretty good at maintaining a wig. If you have any more questions, feel free to ask!