You'd need a combination of a convex and concave lenses. The width of the resultant beam would depend on the angle of incident light, the focal lenghts of the lenses, and how far apart they were placed. The system would work best if you collimated the incident light with a biconvex lense first. The other websites you've looked at complicated the heck out of it because it is not a trivial problem. Sorry. FYI, if you were able to collimate the light (i.e. get all light exiting your focusing system to travel in parallel paths) it still wouldn't technically be a laser becasue it wouldn't be coherent. The best thing you can do other than taking a course in optics is to get a concave and convex lense and play with them by placing them different distance apart. It won't be perfect but it might be good enough depending on what your purpose is.