Now might be a good time to save your creation, so go to the top bar and click File/Save. Choose a location to save it to and a name, then confirm the save.
Now, back to the modelling. Click tab (to the left of q) to go out of edit mode and into object mode. Click z to make the hilt none-transparent. Middle-mouse click and drag to look around your creation. You may note that it's a bit bumpy at the moment, so on the left hand bar click Smooth (pic 1). Deselect all by clicking a, then go shift-a and create yet another cylinder!!! :P. Click z again, then go View/Top (or 7 on the numberpad). Scale it down only very slightly, then go View/Front (or 1 on the numberpad.). Scroll out a bit, then scale along the z axis like in pic 2. Move it upwards using the blue arrow until it sits just below the tip of the hilt, like how a real lego lightsaber would. Add a new material to it, and color it however you want. (Leave the second color bar though: that shows what color it gives off when light shines on it.) Scroll down the material section, and just above the mirror entry is one called transparency. Check the box to allow it, and set it's Fresnel to 1.410. Now we're nearly done: we just need to add a light. Go shift-a, and choose Lamp/Area. You should have something like in pic 3. Click r and type rotate the light so that it's beam points upwards towards the lightsaber blade. Move the light towards the tip of the hilt using the blue arrow. You may have noticed that instead of the Material tab, there's now a Light one, showing the color, light type, shadow etc. of the light. Set the color as the same that you want your lightsaber to be. Ok! You're done! The final thing to do is render the scene. Select the little triangular object in the scene: This is the camera, and it acts as the eye of the modeller. position it like I've show in pic 4. (I had to put two screenshots into one pic, as I didn't have enough pic slots :P) Then click F12 along the top line of your keypad to render. Pic 5 is the final result. There's bound to be some hitchups, so just post a comment if you get stuck :)