I have added a more detailed instructions on the wiki. I hope it is clear now how it should be assembled. Also there is now a small movie of it in operation.
Due mind that getting spot or beams is very tricky. RGB led will not let you do this since the colours needs to be mixed. And that mixing results in frosting. However small beam angles are no problem. I use 15 degrees but the same type of lens can also be 5 degrees. Even with a single colour led the cheap clear plastic optics will not give you sharp beams, so glass optics will be necessary.