Re: Fill layer help =/
Not sure if you're referring to the fill layer or the mask? If you're talking about the fill layer, just make sure your foreground color is black when you create it. Once created, if you want to change the color, just double click the layer thumbnail to bring up the color picker. If you're talking about making the layer mask black, just click on it to make it active and choose Image>Adjustments>Invert or hit Cmd/Ctrl + I