It's important to eliminate the background of the logo so that it is "transparent".
- Save your logo to disk and open it in PSE Editor (expert tab)
- Drag the padlock on the background layer (in the layers palette) to the trash can in order to unlock it
- Set up the magic wand tool with tolerance=32, contiguous unchecked.
- Click on background and hit delete on keyboard. This should remove the background.
- Save logo via File>save for web>PNG 24, transparency checked, .in folder on desktop
- Close PSE
- Start from scratch with a picture
- Open your logo from step 5, and drag it onto the picture (or copy/paste). It will come in as a separate layer in the layers palette.
- Position and resize to suit with move tool.
- The checkerboard pattern that you see surrounding the logo denotes transparency. It will not be visible on the web site. If you wish to remove the black oval, access the eraser tool and erase it.
It is critical to save the logo in a file format which supports transparency.
Further to step #3, you may have to adjust the tolerance value down, but start with default=32.