Hi
This shouldn't be too hard to achieve....
Open up a graphics program - pretty much anyone will do.
Create a new image. I created one about 1024 x 768, but it's not too critical.
Give it a black colour for your background.
Create a new layer. Draw a suitably sized rectangle for your logo to go into.
Select the rectangle (method will vary depending on the graphics program that you are using).
Presuming you already have your logo prepared, open it in the same program and copy it. Then paste into the selected rectaangle mentioned above.
Save it as a png or jpeg to your desktop and then import it into iPhoto.
Open iMovie.
Now, I have an older version of the program but similar arrangements will apply, I'm sure.
Make sure that you have the clip viewer selected (ie NOT Timeline) at the bottom of the screen.
Go to the Media button. Select Photos. You should find the image there.
Apply the Ken Burns effect. Drag the image from the panel to the start of your movie and you're done.
Hope all that makes sense, but if you would like further clarification, let me know. If you succeed, let everyone know!
Cheers Mitcherooney