First, get your TIE (or whatever is firing the laser) into Bryce. Don't position it in scene until you've done the rest of the tutorial. Just leave it at world centre with no rotation. This makes the positioning of the beams MUCH easier!
Now create a sphere. Elongate it like so. Line it up with one of the guns of the TIE.
Switch to a side view, and line the sphere up with the gun.
Copy and paste the sphere, and move the copy over to the other gun.
Select both the beams and click on the little "M" button next to them. This takes us to the Material editor. Go to your Presets menu, and select "Green Lit" from "Complex FX"
You can change the colour of the beam easily enough. Just change all the green colours to the colour you want. I've turned the transparency down a bit here. You can experinent with this to see what you think is best. Now select the drop down (in the pic) and untick "Cast shadows", "Receive Shadows", and "Self Shadows". As the beam is supposed to be a light source, we don't want it casting any shadows!
