I assume the image was done on the white background (not on it's own layer above the white). First thing is to double click on the where it says Background in the Layers palette. CLick OK on the New Layer window that comes up. Use the magic wand on the white to select it and hit delete. Go to Image > Trim > Transparent Pixels with all 4 boxes in Trim Away checked. You will then have to save your image as a gif as jpg can't have a transparent background. File > Save for Web and select GIF. If you still see some white pixels around the edge, you can change the Matte to None and Save.