To remove the white background from an image first you need to make the background layer into a floating layer by double-clicking on the layer name in the layers palette. It will now be named ‘layer 0’ by default.
Next, double-click on the ‘layer 0’ thumbnail in the layers palette to bring up the Layer Styles dialog.
There are two sliders near the bottom of the dialog. It’s the top slider that we are interested in, the one marked ‘this layer’. See the little white pointer underneath the slider on the right? Now hold down the ALT key on PC (Option key on Mac) and click on it. This will split the single pointer in to 2 half pointers. Slowly drag the left sided pointer to the left and watch as the white background disappears. (It may help you to see the effect better if you create a dark or even red coloured layer underneath this layer – as with the refine edge dialog, but this isn’t essential).
You should slide the pointer until the number above the slider reads about 170 to clear all the white but play around with it a bit until you’re satisfied with the right level for your image.