I'm sure a number of the wiser folks in here will give you more advice soon, but I'll start with a couple of points:
* There are a couple of beginner sub-forums here that would be worth going through as you can read what other people have gone through and asked. It'll help as there's also often more detailed explanations about various terms or items, etc.
* If you have access to a astro club or store, you might want to chat with the people there. You may also get to see the setups of other people and see what they do and and why.
* At a minimum, you'll need an adaptor from the Canon 5D to the scope - T-Ring (for example:
http://www.celestron.com/browse-shop...non-eos-camera) - I'm not sure if there are other pieces that will be required to connect to your scope and to get the required spacing needed to focus.
* I can foresee other issues that will quickly arise as you gain experience that will require more gear, but that's a more in-depth discussion and I really think going back through the beginner forums will help.
If I may ask, what made you buy a Celestron CGEM-925?