First of all, the object you're drawing is very confusing with regards to it's exact structure. The whole thing lacks any sort of perspective or indications of how it is put together. This will make it hard for you to add proper tones. How are you supposed to properly shade the object, when you've drawn it in such a way that you can't tell what planes would be hit by the light, and what planes would be parallel to light, and what planes would face away from light?
Perhaps working on the underlying drawing will make shading much easier for you.
Aside from that, I think you're being too shy with shadows. They are very faint right now, and the highlights are non-existent (I think that maybe the light gray squiggles on the random gadgets on the bottom are supposed to be highlights, but I'm not sure). A great way to fix this is to draw from observation instead of imagination. For now anyway. Go look at a car or something similar to your spaceship thingy, and practice values. Practicing in black and white will help you more than practicing in color at first. It's a good way to train yourself to see light and dark without getting sidetracked by which shade of red looks prettiest or whether a lime green window will look cool.
'Cuz life is full of your regrets, and I should be one...