Need logo with transparent background

I have saved my logo design as bitmap with transparent background using PNG extension and uploaded the PNGs several times with no success. I still have a white box/background. Is it possible to have a transparent background for my logo and for the logo to hover over my own header image? Does the Woocommerce Boutique theme allow transparent logo? IF not, is there a theme that allows such? Do I need to learn code in order to accomplish this?
Thanks for help!